Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2017	Oct. 16, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Trading Symbol	CSTR
Entity Registrant Name	CAPSTAR FINANCIAL HOLDINGS, INC.
Entity Central Index Key	0001676479
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		11,359,130

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets
Cash and due from banks	$ 10,796	$ 9,134
Interest-bearing deposits in financial institutions	58,993	54,323
Federal funds sold		16,654
Total cash and cash equivalents	69,789	80,111
Securities available-for-sale, at fair value	146,600	182,355
Securities held-to-maturity, fair value of $48,980, and $49,731 at September 30, 2017 and December 31, 2016, respectively	45,635	46,864
Loans held for sale	53,225	42,111
Loans	974,530	935,251
Less allowance for loan losses	(14,122)	(11,634)
Loans, net	960,408	923,617
Premises and equipment, net	5,978	5,350
Restricted equity securities	8,799	6,032
Accrued interest receivable	3,849	3,942
Goodwill	6,219	6,219
Core deposit intangible	33	71
Deferred tax assets	12,472	12,956
Bank owned life insurance	22,335	21,900
Other assets	3,217	2,147
Total assets	1,338,559	1,333,675
Deposits:
Non-interest-bearing	250,007	197,788
Interest-bearing	303,756	299,621
Savings and money market accounts	338,391	447,686
Time	199,341	183,628
Total deposits	1,091,495	1,128,723
Federal Home Loan Bank advances	95,000	55,000
Accrued interest payable	305	212
Other liabilities	7,555	10,533
Total liabilities	1,194,355	1,194,468
Shareholders’ equity:
Series A convertible preferred stock, $1 par value; 5,000,000 shares authorized; 878,049 shares issued and outstanding at September 30, 2017 and December 31, 2016	878	878
Common stock, voting, $1 par value; 20,000,000 shares authorized; 11,346,498 and 11,204,515 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	11,347	11,205
Additional paid-in capital	117,617	116,143
Retained earnings	18,541	17,132
Accumulated other comprehensive loss, net of income tax	(4,179)	(6,151)
Total shareholders’ equity	144,204	139,207
Total liabilities and shareholders’ equity	$ 1,338,559	$ 1,333,675

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Securities held to maturity, fair value	$ 48,980	$ 49,731
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	878,049	878,049
Preferred stock, shares outstanding	878,049	878,049
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	20,000,000	20,000,000
Common stock, shares issued	11,346,498	11,204,515
Common stock, shares outstanding	11,346,498	11,204,515

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest income:
Loans, including fees	$ 12,095	$ 10,659	$ 33,935	$ 29,532
Securities:
Taxable	838	787	2,827	2,596
Tax-exempt	304	291	944	841
Federal funds sold	7	4	26	12
Restricted equity securities	108	71	271	210
Interest-bearing deposits in financial institutions	169	63	387	197
Total interest income	13,521	11,875	38,390	33,388
Interest expense:
Interest-bearing deposits	635	404	1,839	1,096
Savings and money market accounts	772	689	2,360	2,141
Time deposits	706	546	1,750	1,566
Federal funds purchased	2	13	13	21
Securities sold under agreements to repurchase				1
Federal Home Loan Bank advances	563	97	1,083	280
Total interest expense	2,678	1,749	7,045	5,105
Net interest income	10,843	10,126	31,345	28,283
Provision for loan losses	(195)	1,639	12,900	2,759
Net interest income after provision for loan losses	11,038	8,487	18,445	25,524
Noninterest income:
Treasury management and other deposit service charges	427	277	1,097	805
Loan commitment fees	223	329	646	901
Net gain (loss) on sale of securities	9	(4)	42	121
Tri-Net fees	367		748
Mortgage banking income	2,030	2,339	4,617	5,342
Other noninterest income	316	250	1,021	961
Total noninterest income	3,372	3,191	8,171	8,130
Noninterest expense:
Salaries and employee benefits	5,119	5,119	14,989	15,275
Data processing and software	709	627	2,040	1,831
Professional fees	336	391	1,050	1,148
Occupancy	531	352	1,518	1,133
Equipment	564	458	1,604	1,301
Regulatory fees	270	250	877	742
Other operating	946	1,330	2,988	3,057
Total noninterest expense	8,475	8,527	25,066	24,487
Income before income taxes	5,935	3,151	1,550	9,167
Income tax expense	1,516	1,042	141	2,998
Net income	$ 4,419	$ 2,109	$ 1,409	$ 6,169
Per share information:
Basic net income per share of common stock	$ 0.39	$ 0.24	$ 0.13	$ 0.71
Diluted net income per share of common stock	$ 0.35	$ 0.20	$ 0.11	$ 0.58
Weighted average shares outstanding:
Basic	11,279,364	8,792,665	11,239,093	8,701,596
Diluted	12,750,423	10,799,536	12,758,091	10,682,976

Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 4,419	$ 2,109	$ 1,409	$ 6,169
Unrealized gains (losses) on securities available-for-sale:
Unrealized holding gains (losses) arising during the period	526	(744)	2,433	2,829
Reclassification adjustment for gains (losses) included in net income	(9)	4	(42)	(121)
Tax effect	(198)	283	(915)	(1,037)
Net of tax	319	(457)	1,476	1,671
Unrealized losses on securities transferred to held-to-maturity:
Reclassification adjustment for losses included in net income	79	42	162	125
Tax effect	(30)	(16)	(62)	(48)
Net of tax	49	26	100	77
Unrealized gains (losses) on cash flow hedges:
Unrealized holding gains (losses) arising during the period	(29)	87	(242)	(1,760)
Reclassification adjustment for losses included in net income	278	88	589	261
Tax effect	(34)	(33)	49	674
Net of tax	215	142	396	(825)
Other comprehensive income (loss)	583	(289)	1,972	923
Comprehensive income	$ 5,002	$ 1,820	$ 3,381	$ 7,092

Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2015	$ 108,586	$ 1,610	$ 8,577	$ 95,277	$ 8,036	$ (4,914)
Beginning balance, shares at Dec. 31, 2015			8,577,051
Issuance of restricted common stock, net of forfeitures and withholdings to satisfy employee tax obligations	(16)		$ 107	(123)
Issuance of restricted common stock, net of forfeitures and withholdings to satisfy employee tax obligations, shares			106,548
Stock-based compensation expense	643			643
Excess tax benefit from stock compensation	29			29
Issuance of common stock	21,928		$ 1,688	20,240
Issuance of common stock, shares			1,688,049
Conversion of preferred stock		(732)	$ 732
Conversion of preferred stock, shares			731,707
Exercise of common stock warrants	165		$ 88	77
Exercise of common stock warrants, shares			87,666
Net income	6,169				6,169
Other comprehensive income	923					923
Ending balance at Sep. 30, 2016	138,427	878	$ 11,192	116,143	14,205	(3,991)
Ending balance, shares at Sep. 30, 2016			11,191,021
Beginning balance at Dec. 31, 2016	139,207	878	$ 11,205	116,143	17,132	(6,151)
Beginning balance, shares at Dec. 31, 2016			11,204,515
Issuance of restricted common stock, net of forfeitures and withholdings to satisfy employee tax obligations	(264)		$ 21	(285)
Issuance of restricted common stock, net of forfeitures and withholdings to satisfy employee tax obligations, shares			21,480
Stock-based compensation expense	771			771
Exercise of employee common stock options, net of withholdings to satisfy employee tax obligations	644		$ 72	572
Exercise of employee common stock options, net of withholdings to satisfy employee tax obligations, shares			71,517
Exercise of common stock warrants	465		$ 49	416
Exercise of common stock warrants, shares			48,986
Net income	1,409				1,409
Other comprehensive income	1,972					1,972
Ending balance at Sep. 30, 2017	$ 144,204	$ 878	$ 11,347	$ 117,617	$ 18,541	$ (4,179)
Ending balance, shares at Sep. 30, 2017			11,346,498

Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 1,409,000	$ 6,169,000
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Provision for loan losses	12,900,000	2,759,000
Accretion of discounts on acquired loans and deferred fees	(537,000)	(1,232,000)
Depreciation and amortization	345,000	324,000
Net amortization of premiums on investment securities	984,000	1,106,000
Securities gains, net	(42,000)	(121,000)
Mortgage banking income	(4,617,000)	(5,342,000)
Tri-Net fees	(748,000)
Net gain on sale of loans	(67,000)
Net loss on disposal of premises and equipment	137,000
Net gain on sale of other real estate owned		(157,000)
Stock-based compensation	771,000	643,000
Excess tax benefit from stock compensation		(29,000)
Deferred income tax expense	(445,000)	63,000
Origination of loans held for sale	(409,179,000)	(393,378,000)
Proceeds from loans held for sale	403,497,000	370,374,000
Net increase in accrued interest receivable and other assets	(1,320,000)	(2,021,000)
Net increase (decrease) in accrued interest payable and other liabilities	(2,630,000)	1,077,000
Net cash provided by (used in) operating activities	458,000	(19,765,000)
Activities in securities available for sale:
Purchases	(11,754,000)	(55,862,000)
Sales	34,299,000	46,700,000
Maturities, prepayments and calls	14,718,000	17,113,000
Activities in securities held to maturity:
Purchases		(4,300,000)
Maturities, prepayments and calls	1,332,000	1,233,000
Purchase of restricted equity securities	(2,767,000)	(112,000)
Net increase in loans	(49,154,000)	(112,961,000)
Purchase of premises and equipment	(1,074,000)	(103,000)
Proceeds from the sale of premises and equipment	3,000
Proceeds from sale of other real estate		373,000
Net cash used in investing activities	(14,397,000)	(107,919,000)
Cash flows from financing activities:
Net increase (decrease) in deposits	(37,228,000)	97,599,000
Proceeds from Federal Home Loan Bank advances	135,000,000	15,000,000
Payments on Federal Home Loan Bank advances	(95,000,000)	(30,000,000)
Issuance of common stock		21,928,000
Exercise of common stock options and warrants, net of repurchase of restricted shares	845,000	149,000
Excess tax benefit from stock compensation		29,000
Net decrease in repurchase agreements		(3,755,000)
Net cash provided by financing activities	3,617,000	100,950,000
Net decrease in cash and cash equivalents	(10,322,000)	(26,734,000)
Cash and cash equivalents at beginning of period	80,111,000	100,185,000
Cash and cash equivalents at end of period	69,789,000	73,451,000
Supplemental disclosures of cash paid:
Interest paid	6,951,000	5,079,000
Income taxes	2,142,000	2,545,000
Supplemental disclosures of noncash transactions:
Loans charged off to the allowance for loan losses	$ 12,369,000	1,452,000
Loans transferred from held for sale to held for investment		$ 2,823,000

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE 1 – SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited consolidated financial statements as of and for the period ended September 30, 2017 include CapStar Financial Holdings, Inc. and its wholly owned subsidiary, CapStar Bank (the “Bank”, together referred to as the “Company”). Significant intercompany transactions and accounts are eliminated in consolidation. On February 5, 2016, CapStar Financial Holdings, Inc. acquired all of the Bank’s issued and outstanding shares of common stock, preferred stock, common stock options and warrants, and the Bank became the wholly owned subsidiary of CapStar Financial Holdings, Inc. The accompanying unaudited consolidated financial statements have been prepared in accordance with instructions to Form 10-Q and do not include all information and footnotes required by U.S. generally accepted accounting principles (“U.S. GAAP”) for complete financial statements. All adjustments consisting of normally recurring accruals that, in the opinion of management, are necessary for a fair presentation of the financial position and results of operations for the periods presented have been included. These unaudited consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements and related notes appearing in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016. Initial Public Offering On September 21, 2016, the Securities and Exchange Commission (“SEC”) declared effective our registration statement on Form S-1 registering the shares of our common stock. On September 27, 2016, we completed the initial public offering of 2,972,750 shares of our common stock. Of the 2,972,750 shares sold, 1,688,049 shares were sold by us and 1,284,701 shares were sold by certain selling shareholders. Of the 1,284,701 shares sold by certain selling shareholders, 731,707 were from preferred shares converted to common shares and 79,166 from the cashless exercise of 250,000 common share warrants. We received net proceeds of approximately $21.9 million from the offering, after deducting the underwriting discounts and commissions and estimated offering expenses. We did not receive any proceeds from the sale of shares by the selling shareholders. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Material estimates that are particularly susceptible to significant change relate to the determination of the allowance for loan losses, determination of impairment of intangible assets, including goodwill, the valuation of our investment portfolio, deferred tax assets and estimated liabilities. There have been no significant changes to the Company’s critical accounting policies as disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016. Tri-Net Fees Tri-Net fees represent a new line of business, implemented in the fourth quarter of 2016, which originates, with the intent to sell, commercial real estate loans to third-party investors. All of these loan sales transfer servicing rights to the buyer. Realized gains and losses are recognized when legal title of the loan has transferred to the investor and sales proceeds have been received and are reflected in the accompanying statement of income in Tri-Net fees, net of related costs such as commission expenses. Loans that have not been sold at period end are classified as held for sale on the balance sheet and recorded at the lower of aggregate cost or fair value. Net unrealized losses, if any, are recorded as a valuation allowance and charged to earnings. Subsequent Events Accounting Standards Codification (“ASC”) 855, Subsequent Events, establishes general standards of accounting for and disclosure of events that occur after the balance sheet date but before financial statements are issued. The Company evaluated all events or transactions that occurred after September 30, 2017 through the date of the issued financial statements.

Securities

9 Months Ended

Sep. 30, 2017

Investments Debt And Equity Securities [Abstract]

Securities

NOTE 2 – SECURITIES

The amortized cost and fair value of securities available-for-sale and held-to-maturity at September 30, 2017 and December 31, 2016 are summarized as follows (dollars in thousands):

	September 30, 2017									December 31, 2016
	Amortized Cost		Gross unrealized gains		Gross unrealized (losses)			Estimated fair value		Amortized Cost		Gross unrealized gains		Gross unrealized (losses)			Estimated fair value
Securities available-for-sale:
U. S. government agency securities	$	11,434	$	18	$	(153	)	$	11,299	$	9,517	$	—	$	(143	)	$	9,374
State and municipal securities		19,031		172		(136	)		19,067		28,480		65		(632	)		27,913
Mortgage-backed securities		96,975		14		(1,166	)		95,823		126,637		17		(2,059	)		124,595
Asset-backed securities		20,668		—		(257	)		20,411		21,620		—		(1,147	)		20,473
Total	$	148,108	$	204	$	(1,712	)	$	146,600	$	186,254	$	82	$	(3,981	)	$	182,355
Securities held-to-maturity:
State and municipal securities	$	36,469	$	3,138	$	—		$	39,607	$	36,842	$	2,784	$	—		$	39,626
Mortgage-backed securities		3,837		77		—			3,914		4,687		79		—			4,766
Other debt securities		5,329		130		—			5,459		5,335		11		(7	)		5,339
Total	$	45,635	$	3,345	$	—		$	48,980	$	46,864	$	2,874	$	(7	)	$	49,731

Security fair values are established by an independent pricing service as of the dates indicated. The difference between amortized cost and fair value reflects current interest rates and represents the potential gain (loss) had the portfolio been liquidated on those dates. Security gains (losses) are realized only in the event of dispositions prior to maturity or other-than-temporary impairment. Securities with unrealized losses as of September 30, 2017 and December 31, 2016, and the length of time they were in continuous loss positions as of such dates are as follows (in thousands):

	Less than 12 months					12 months or more					Total
September 30, 2017	Estimated fair value		Gross unrealized losses			Estimated fair value		Gross unrealized losses			Estimated fair value		Gross unrealized losses
U. S. government agency securities	$	9,303	$	(153	)	$	—	$	—		$	9,303	$	(153	)
State and municipal securities		4,968		(19	)		6,103		(117	)		11,071		(136	)
Mortgage-backed securities		61,997		(591	)		30,360		(575	)		92,357		(1,166	)
Asset-backed securities		—		—			20,410		(257	)		20,410		(257	)
Total temporarily impaired securities	$	76,268	$	(763	)	$	56,873	$	(949	)	$	133,141	$	(1,712	)

December 31, 2016
U. S. government agency securities	$	9,374	$	(143	)	$	—	$	—		$	9,374	$	(143	)
State and municipal securities		20,279		(632	)		—		—			20,279		(632	)
Mortgage-backed securities		110,563		(1,955	)		4,150		(104	)		114,713		(2,059	)
Asset-backed securities		—		—			20,473		(1,147	)		20,473		(1,147	)
Other debt securities		2,029		(7	)		—		—			2,029		(7	)
Total temporarily impaired securities	$	142,245	$	(2,737	)	$	24,623	$	(1,251	)	$	166,868	$	(3,988	)

As noted in the table above, as of September 30, 2017, the Company had unrealized losses of $1.7 million in its investment securities portfolio. The unrealized losses associated with these investment securities are driven by changes in interest rates and are recorded as a component of equity. These investment securities will continue to be monitored as a part of our ongoing impairment analysis. Management evaluates the financial performance of the issuers on a quarterly basis to determine if it is probable that the issuers can make all contractual principal and interest payments. If a shortfall in future cash flows is identified, a credit loss will be deemed to have occurred and will be recognized as a charge to earnings and a new cost basis for the security will be established.

Because the Company currently does not intend to sell any investment securities that have an unrealized loss at September 30, 2017, and it is not more-likely-than-not that we will be required to sell these investment securities before recovery of their amortized cost bases, which may be at maturity, we do not consider these securities to be other-than-temporarily impaired at September 30, 2017.

Securities with a carrying value of $127.1 million at September 30, 2017 were pledged to collateralize public deposits, derivative positions and Federal Home Loan Bank advances.

The proceeds from sales of securities and the associated gains and losses are listed below (dollars in thousands):

	Nine Months Ended			Nine Months Ended
	September 30, 2017			September 30, 2016
Proceeds	$	34,299		$	46,700
Gross gains		99			244
Gross losses		(57	)		(123	)

The amortized cost and fair value of securities at September 30, 2017, by contractual maturity, are shown below (dollars in thousands). Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Securities not due at a single maturity date are shown separately.

	Available-for-sale				Held-to-maturity
	Amortized cost		Estimated fair value		Amortized cost		Estimated fair value
Due one to five years	$	11,388	$	11,511	$	27,299	$	29,448
Due five to ten years		17,970		17,788		14,069		15,129
Due beyond ten years		1,107		1,067		430		489
Mortgage-backed securities		96,975		95,823		3,837		3,914
Asset-backed securities		20,668		20,411		—		—
	$	148,108	$	146,600	$	45,635	$	48,980

Loans and Allowance for Loan Losses

9 Months Ended

Sep. 30, 2017

Receivables [Abstract]

Loans and Allowance for Loan Losses

NOTE 3 – LOANS AND ALLLOWANCE FOR LOAN LOSSES

A summary of the loan portfolio as of September 30, 2017 and December 31, 2016 follows (dollars in thousands):

	September 30, 2017			December 31, 2016
Commercial real estate	$	366,778		$	302,322
Consumer real estate		100,811			97,015
Construction and land development		79,951			94,491
Commercial and industrial		394,600			379,620
Consumer		6,289			5,974
Other		26,460			56,796
Total		974,889			936,218
Less net unearned income		(359	)		(967	)
		974,530			935,251
Allowance for loan losses		(14,122	)		(11,634	)
	$	960,408		$	923,617

The adequacy of the allowance for loan losses (ALL) is assessed at the end of each quarter. The ALL includes a specific component related to loans that are individually evaluated for impairment and a general component related to loans that are segregated into homogenous pools and collectively evaluated for impairment. The ALL factors applied to these pools are an estimate of probable incurred losses based on management’s evaluation of historical net losses from loans with similar characteristics, which are adjusted by management to reflect current events, trends, and conditions. The adjustments include consideration of the following: changes in lending policies and procedures, economic conditions, nature and volume of the portfolio, experience of lending management, volume and severity of past due loans, quality of the loan review system, value of underlying collateral for collateral dependent loans, concentrations, and other external factors.

The Company categorizes loans into risk categories based on relevant information about the ability of borrowers to service their debt such as: current financial information, historical payment experience, credit documentation, public information, and current economic trends, among other factors. The Company analyzes all commercial loans, and consumer relationships with an outstanding balance greater than $500,000, individually and assigns each loan a risk rating. This analysis is performed on a continual basis by the relationship managers and credit department personnel. On at least an annual basis an independent party performs a formal credit risk review of a sample of the loan portfolio. Among other things, this review assesses the appropriateness of the loan’s risk rating. The Company uses the following definitions for risk ratings:

Special Mention – A special mention asset possesses deficiencies or potential weaknesses deserving of management’s attention. If uncorrected, such weaknesses or deficiencies may expose the Company to an increased risk of loss in the future.

Substandard – A substandard asset is inadequately protected by the current sound net worth and paying capacity of the obligor or of the collateral pledged, if any. Assets so classified must have a well-defined weakness or weaknesses that jeopardize the liquidation of the debt. They are characterized by the distinct possibility that the Company will sustain some loss if deficiencies are not corrected. Loss potential, while existing in the aggregate amount of substandard assets, does not have to exist in individual assets classified substandard.

Doubtful – A doubtful asset has all weaknesses inherent in one classified substandard, with the added characteristic that weaknesses make collection or liquidation in full, on the basis of existing facts, conditions, and values, highly questionable and improbable. The probability of loss is extremely high, but certain important and reasonable specific pending factors which may work to the advantage and strengthening of the asset exist, therefore, its classification as an estimated loss is deferred until a more exact status may be determined. Pending factors include proposed merger, acquisition or liquidation procedures, capital injection, perfecting liens on additional collateral, and refinancing plans.

Loans not falling into the criteria above are considered to be pass-rated loans. The Company utilizes six loan grades within the pass risk rating.

The following tables present the loan balances by category as well as risk rating (dollars in thousands):

	Performing Loans
September 30, 2017	Pass/Watch		Special Mention		Substandard		Total Performing		Total Impaired Loans		Total
Commercial real estate	$	365,545	$	—	$	—	$	365,545	$	1,233	$	366,778
Consumer real estate		100,522		—		289		100,811		—		100,811
Construction and land development		79,951		—		—		79,951		—		79,951
Commercial and industrial		370,657		16,443		5,568		392,668		1,932		394,600
Consumer		6,276		—		13		6,289		—		6,289
Other		26,460		—		—		26,460		—		26,460
Total	$	949,411	$	16,443	$	5,870	$	971,724	$	3,165	$	974,889

December 31, 2016
Commercial real estate	$	301,012	$	—	$	—	$	301,012	$	1,310	$	302,322
Consumer real estate		96,722		—		293		97,015		—		97,015
Construction and land development		94,491		—		—		94,491		—		94,491
Commercial and industrial		349,857		11,035		16,419		377,311		2,309		379,620
Consumer		5,958		—		16		5,974		—		5,974
Other		56,796		—		—		56,796		—		56,796
Total	$	904,836	$	11,035	$	16,728	$	932,599	$	3,619	$	936,218

None of the Company’s loans had a risk rating of “Doubtful” as of September 30, 2017 or December 31, 2016.

The following tables detail the changes in the ALL for the three and nine months ended September 30, 2017 and 2016 (in thousands):

	Commercial real estate			Consumer real estate			Construction and land development		Commercial and industrial			Consumer			Other			Total
Three Months Ended September 30, 2017
Balance, beginning of period	$	3,533		$	1,081		$	911	$	6,395		$	57		$	477		$	12,454
Charged-off loans		—			—			—		—			—			—			—
Recoveries		3			—			—		1,860			—			—			1,863
Provision for loan losses		(242	)		(97	)		576		(306	)		22			(148	)		(195	)
Balance, end of period	$	3,294		$	984		$	1,487	$	7,949		$	79		$	329		$	14,122

Three Months Ended September 30, 2016
Balance, beginning of period	$	2,596		$	968		$	943	$	5,037		$	104		$	806		$	10,454
Charged-off loans		—			—			—		(645	)		—						(645	)
Recoveries		52			—			—		10			—			—			62
Provision for loan losses		(228	)		4			721		1,166			(18	)		(6	)		1,639
Balance, end of period	$	2,420		$	972		$	1,664	$	5,568		$	86		$	800		$	11,510

	Commercial real estate			Consumer real estate			Construction and land development			Commercial and industrial			Consumer			Other			Total
Nine Months Ended September 30, 2017
Balance, beginning of period	$	2,655		$	1,013		$	1,574		$	5,618		$	76		$	698		$	11,634
Charged-off loans		—			—			—			(12,369	)		—			—			(12,369	)
Recoveries		4			—			—			1,862			91			—			1,957
Provision for loan losses		635			(29	)		(87	)		12,838			(88	)		(369	)		12,900
Balance, end of period	$	3,294		$	984		$	1,487		$	7,949		$	79		$	329		$	14,122

Nine Months Ended September 30, 2016
Balance, beginning of period	$	2,879		$	968		$	914		$	4,693		$	103		$	575		$	10,132
Charged-off loans		(350	)		—			—			(956	)		(146	)		—			(1,452	)
Recoveries		52			—			—			18			1			—			71
Provision for loan losses		(161	)		4			750			1,813			128			225			2,759
Balance, end of period	$	2,420		$	972		$	1,664		$	5,568		$	86		$	800		$	11,510

A breakdown of the ALL and the loan portfolio by loan category at September 30, 2017 and December 31, 2016 follows (dollars in thousands):

	Commercial real estate		Consumer real estate		Construction and land development		Commercial and industrial		Consumer		Other		Total
September 30, 2017
Allowance for Loan Losses:
Collectively evaluated for impairment	$	3,294	$	984	$	1,487	$	7,449	$	79	$	329	$	13,622
Individually evaluated for impairment		—		—		—		500		—		—		500
Balances, end of period	$	3,294	$	984	$	1,487	$	7,949	$	79	$	329	$	14,122
Loans:
Collectively evaluated for impairment	$	365,545	$	100,811	$	79,951	$	392,668	$	6,289	$	26,460	$	971,724
Individually evaluated for impairment		1,233		—		—		1,932		—		—		3,165
Balances, end of period	$	366,778	$	100,811	$	79,951	$	394,600	$	6,289	$	26,460	$	974,889

December 31, 2016
Allowance for Loan Losses:
Collectively evaluated for impairment	$	2,655	$	1,013	$	1,574	$	5,118	$	76	$	698	$	11,134
Individually evaluated for impairment		—		—		—		500		—		—		500
Balances, end of period	$	2,655	$	1,013	$	1,574	$	5,618	$	76	$	698	$	11,634
Loans:
Collectively evaluated for impairment	$	301,012	$	97,015	$	94,491	$	377,311	$	5,974	$	56,796	$	932,599
Individually evaluated for impairment		1,310		—		—		2,309		—		—		3,619
Balances, end of period	$	302,322	$	97,015	$	94,491	$	379,620	$	5,974	$	56,796	$	936,218

The following table presents the allocation of the ALL for each respective loan category with the corresponding percentage of the ALL in each category to total loans, net of deferred fees as of September 30, 2017 and December 31, 2016 (dollars in thousands):

	September 30, 2017					December 31, 2016
	Amount		Percent of total loans, net of deferred fees			Amount		Percent of total loans, net of deferred fees
Commercial real estate	$	3,294		0.34	%	$	2,655		0.28	%
Consumer real estate		984		0.10			1,013		0.11
Construction and land development		1,487		0.15			1,574		0.17
Commercial and industrial		7,949		0.82			5,618		0.60
Consumer		79		0.01			76		0.01
Other		329		0.03			698		0.07
Total allowance for loan losses	$	14,122		1.45	%	$	11,634		1.24	%

The following table presents the Company’s impaired loans that were evaluated for specific loss allowance as of September 30, 2017 and December 31, 2016 (dollars in thousands):


	September 30, 2017						December 31, 2016
	Recorded investment		Unpaid principal balance		Related allowance		Recorded investment		Unpaid principal balance		Related allowance
With no related allowance recorded:
Commercial real estate	$	1,233	$	1,660	$	—	$	1,310	$	1,686	$	—
Consumer real estate		—		—		—		—		—		—
Construction and land development		—		—		—		—		—		—
Commercial and industrial		—		—		—		—		—		—
Consumer		—		—		—		—		—		—
Other		—		—		—		—		—		—
Subtotal		1,233		1,660		—		1,310		1,686		—
With an allowance recorded:
Commercial real estate		—		—		—		—		—		—
Consumer real estate		—		—		—		—		—		—
Construction and land development		—		—		—		—		—		—
Commercial and industrial		1,932		2,770		500		2,309		2,921		500
Consumer		—		—		—		—		—		—
Other		—		—		—		—		—		—
Subtotal		1,932		2,770		500		2,309		2,921		500
Total	$	3,165	$	4,430	$	500	$	3,619	$	4,607	$	500

The following table presents information related to the average recorded investment and interest income recognized on impaired loans for the three and nine months ended September 30, 2017 and 2016 (dollars in thousands):

	Three Months Ended				Three Months Ended				Nine Months Ended				Nine Months Ended
	September 30, 2017				September 30, 2016				September 30, 2017				September 30, 2016
	Average recorded investment		Interest income recognized		Average recorded investment		Interest income recognized		Average recorded investment		Interest income recognized		Average recorded investment		Interest income recognized
With no related allowance recorded:
Commercial real estate	$	1,245	$	—	$	—	$	—	$	1,272	$	—	$	—	$	—
Consumer real estate		—		—		—		—		—		—		—		—
Construction and land development		—		—		—		—		—		—		—		—
Commercial and industrial		—		—		—		—		—		—		—		—
Consumer		—		—		—		—		—		—		—		—
Other		—		—		—		—		—		—		—		—
Subtotal		1,245		—		—		—		1,272		—		—		—
With an allowance recorded:
Commercial real estate		—		—		1,685		—		—		—		1,742		—
Consumer real estate		—		—		—		—		—		—		—		—
Construction and land development		—		—		—		—		—		—		—		—
Commercial and industrial		1,941		—		3,411		—		2,141		—		3,534		30
Consumer		—		—		—		—		—		—		—		—
Other		—		—		—		—		—		—		—		—
Subtotal		1,941		—		5,096		—		2,141		—		5,276		30
Total	$	3,186	$	—	$	5,096	$	—	$	3,413	$	—	$	5,276	$	30

There was no interest income recognized on a cash basis for impaired loans for the three or nine months ended September 30, 2017 or 2016.

The following table presents the aging of the recorded investment in past-due loans as of September 30, 2017 and December 31, 2016 by class of loans (dollars in thousands):

	30 - 59		60 - 89		Greater Than
	Days		Days		89 Days		Total		Loans Not
	Past Due		Past Due		Past Due		Past Due		Past Due		Total
September 30, 2017
Commercial real estate	$	—	$	—	$	—	$	—	$	366,778	$	366,778
Consumer real estate		506		279		—		785		100,026		100,811
Construction and land development		—		—		—		—		79,951		79,951
Commercial and industrial		1,154		218		27		1,398		393,202		394,600
Consumer		—		1		—		1		6,288		6,289
Other		—		—		—		—		26,460		26,460
Total	$	1,660	$	497	$	27	$	2,184	$	972,705	$	974,889

December 31, 2016
Commercial real estate	$	—	$	—	$	—	$	—	$	302,322	$	302,322
Consumer real estate		81		282		—		363		96,652		97,015
Construction and land development		—		—		—		—		94,491		94,491
Commercial and industrial		—		—		—		—		379,620		379,620
Consumer		—		—		—		—		5,974		5,974
Other		—		—		—		—		56,796		56,796
Total	$	81	$	282	$	—	$	363	$	935,855	$	936,218

The following table presents the recorded investment in non-accrual loans, past due loans over 90 days outstanding and accruing and troubled debt restructurings (“TDR”) by class of loans as of September 30, 2017 and December 31, 2016 (dollars in thousands):

	Non-Accrual		Past Due Over 90 Days and Accruing		Troubled Debt Restructurings
September 30, 2017
Commercial real estate	$	1,233	$	—	$	1,222
Consumer real estate		—		—		—
Construction and land development		—		—		—
Commercial and industrial		1,932		27		—
Consumer		—		—		—
Other		—		—		—
Total	$	3,165	$	27	$	1,222

December 31, 2016
Commercial real estate	$	1,310	$	—	$	1,272
Consumer real estate		—		—		—
Construction and land development		—		—		—
Commercial and industrial		2,309		—		—
Consumer		—		—		—
Other		—		—		—
Total	$	3,619	$	—	$	1,272

As of September 30, 2017 and December 31, 2016, all loans classified as nonperforming were deemed to be impaired.

As of September 30, 2017 and December 31, 2016, the Company had a recorded investment in TDR of $1.2 million and $1.3 million, respectively. The Company had no specific allowance for those loans at September 30, 2017 or December 31, 2016 and there were no commitments to lend additional amounts. Loans accounted for as TDR include modifications from original terms such as those due to bankruptcy proceedings, certain modifications of amortization periods or extended suspension of principal payments due to customer financial difficulties. In order to determine whether a borrower is experiencing financial difficulty, an evaluation is performed of the probability that the borrower will be in payment default on any of its debt in the foreseeable future without the modification. This evaluation is performed under the Bank’s loan policy. Loans accounted for as TDR are individually evaluated for impairment.

The following table presents loans by class modified as TDR that occurred during the three and nine months ended September 30, 2016 (dollars in thousands). There were no new TDR identified during the three or nine months ended September 30, 2017.

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	Number of contracts		Pre modification outstanding recorded investment		Post modification outstanding recorded investment, net of related allowance		Number of contracts		Pre modification outstanding recorded investment		Post modification outstanding recorded investment, net of related allowance
2016
Commercial real estate		—	$	—	$	—		1	$	1,948	$	1,170
Consumer real estate		—		—		—		—		—		—
Construction and land development		—		—		—		—		—		—
Commercial and industrial		—		—		—		—		—		—
Consumer		—		—		—		—		—		—
Other		—		—		—		—		—		—
Total		—	$	—	$	—		1	$	1,948	$	1,170

The following table presents loans by class modified as TDR for which there was a payment default within twelve months following the modification during the three and nine months ended September 30, 2016 (dollars in thousands). There were no TDR for which there was a payment default within twelve months following the modification during the three or nine months ended September 30, 2017.

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	Number of contracts		Recorded investment		Number of contracts		Recorded investment
2016
Commercial real estate		—	$	—		—	$	—
Consumer real estate		—		—		—		—
Construction and land development		—		—		—		—
Commercial and industrial		—		—		—		—
Consumer		—		—		1		124
Other		—		—		—		—
Total		—	$	—		1	$	124

The consumer loan TDR that subsequently defaulted during the nine months ended September 30, 2016 had no specific reserve in the allowance for loan losses and resulted in a $0.1 million charge-off.

A loan is considered to be in payment default once it is 30 days contractually past due under the modified terms.

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Federal Home Loan Bank Advances

9 Months Ended

Sep. 30, 2017

Federal Home Loan Banks [Abstract]

Federal Home Loan Bank Advances

NOTE 4 – FEDERAL HOME LOAN BANK ADVANCES

The Company had outstanding borrowings totaling $95.0 million and $55.0 million at September 30, 2017 and December 31, 2016, respectively, via various advances. These advances are non-callable; interest payments are due monthly, with principal due at maturity.

The following is a summary of the contractual maturities and average effective rates of outstanding advances (dollars in thousands):

	September 30, 2017					December 31, 2016
Year	Amount		Interest Rates			Amount		Interest Rates
2017	$	60,000		1.18	%	$	55,000		0.80	%
2018		35,000		1.50			—		—
2019		—		—			—		—
2020		—		—			—		—
2021		—		—			—		—
Thereafter		—		—			—		—
Total	$	95,000		1.30	%	$	55,000		0.80	%

Advances from the FHLB are collateralized by investment securities, FHLB stock and certain commercial and residential real estate mortgage loans totaling $367.0 million under a blanket mortgage collateral agreement. At September 30, 2017, the amount of available credit from the FHLB totaled $108.0 million.

Accumulated Other Comprehensive Income (Loss)

9 Months Ended

Sep. 30, 2017

Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]

Accumulated Other Comprehensive Income (Loss)

NOTE 5 – ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)

The following were changes in accumulated other comprehensive income (loss) by component, net of tax, for the nine months ended September 30, 2017 and 2016 (dollars in thousands):

				Unrealized Gains			Unrealized
	Gains and			and Losses			Losses on
	Losses on			on Available			Securities
	Cash Flow			for Sale			Transferred to
	Hedges			Securities			Held to Maturity			Total
Nine Months Ended September 30, 2017
Beginning Balance	$	(4,241	)	$	(698	)	$	(1,212	)	$	(6,151	)
Other comprehensive income (loss) before reclassification, net of tax		(193	)		1,502			—			1,309
Amounts reclassified from accumulated other comprehensive income (loss), net of tax		589			(26	)		100			663
Net current period other comprehensive income (loss)		396			1,476			100			1,972
Ending Balance	$	(3,845	)	$	778		$	(1,112	)	$	(4,179	)

Nine Months Ended September 30, 2016
Beginning Balance	$	(3,704	)	$	105		$	(1,315	)	$	(4,914	)
Other comprehensive income (loss) before reclassification, net of tax		(1,086	)		1,746			—			660
Amounts reclassified from accumulated other comprehensive income (loss), net of tax		261			(75	)		77			263
Net current period other comprehensive income (loss)		(825	)		1,671			77			923
Ending Balance	$	(4,529	)	$	1,776		$	(1,238	)	$	(3,991	)

The following were significant amounts reclassified out of each component of accumulated other comprehensive income (loss) for the three and nine months ended September 30, 2017 and 2016 (dollars in thousands):

													Affected Line Item
Details about Accumulated Other	Three Months Ended September 30,						Nine Months Ended September 30,						in the Statement Where
Comprehensive Income Components	2017			2016			2017			2016			Net Income is Presented
Unrealized losses on cash flow hedges	$	109		$	38		$	322		$	113		Interest expense - money market
		168			50			267			148		Interest expense - Federal Home Loan Bank advances
	$	277		$	88		$	589		$	261		Net of tax
Unrealized (gains) and losses on available for sale securities	$	(9	)	$	4		$	(42	)	$	(121	)	Net (gain) loss on sale of securities
		3			(2	)		16			46		Income tax expense (benefit)
	$	(6	)	$	2		$	(26	)	$	(75	)	Net of tax
Unrealized losses on securities transferred to held to maturity	$	79		$	42		$	162		$	125		Interest income - securities
		(30	)		(16	)		(62	)		(48	)	Income tax benefit
	$	49		$	26		$	100		$	77		Net of tax

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 6 – INCOME TAXES The Company’s effective tax rate for the three and nine months ended September 30, 2017 was 25.5% and 9.1% compared to 33.1% and 32.7% for the three and nine months ended September 30, 2016. In March 2016, the FASB issued guidance to simplify several aspects of the accounting for share-based payment award transactions, including income tax consequences. In addition to other changes, the guidance changes the accounting for excess tax benefits and tax deficiencies from generally being recognized in additional paid-in capital to recognition as income tax expense or benefit in the period they occur. The Company adopted the new guidance in the first quarter of 2017. As a result, the Company’s income tax expense was reduced by $144,000 and $310,000 for the three and nine months ended September 30, 2017. The effective tax rate compared favorably to the statutory federal rate of 34% and Tennessee excise tax rate of 6.5% primarily due to investments in qualified municipal securities, company owned life insurance, state tax credits, net of the effect of certain non-deductible expenses and the recognition of excess tax benefits related to stock compensation.

Commitments and Contingencies

9 Months Ended

Sep. 30, 2017

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

NOTE 7 – COMMITMENTS AND CONTINGENCIES

In the normal course of business, the Company has outstanding commitments and contingent liabilities, such as commitments to extend credit and standby letters of credit, which are not included in the accompanying financial statements. The Company’s exposure to credit loss in the event of nonperformance by the other party to the financial instruments for commitments to extend credit and standby letters of credit is represented by the contractual or notional amount of those instruments. The Company uses the same credit policies in making such commitments as it does for instruments that are included in the balance sheet.

The following table sets forth outstanding financial instruments whose contract amounts represent credit risk as of September 30, 2017 and December 31, 2016 (dollars in thousands):

	Contract or notional amount
	September 30, 2017		December 31, 2016
Financial instruments whose contract amounts represent credit risk:
Unused commitments to extend credit	$	575,558	$	508,990
Standby letters of credit		11,535		10,886
Total	$	587,093	$	519,876

The Company is party to litigation and claims arising in the normal course of business. Management believes that the liabilities, if any, arising from such litigation and claims as of September 30, 2017, will not have a material impact on the financial statements of the Company.

Derivatives

9 Months Ended

Sep. 30, 2017

Derivative Instruments And Hedging Activities Disclosure [Abstract]

Derivatives

NOTE 8 – DERIVATIVES

The Company utilizes interest rate swap agreements as part of its asset liability management strategy to help manage its interest rate risk position. The notional amount of the interest rate swaps does not represent amounts exchanged by the parties. The amount exchanged is determined by reference to the notional amount and the other terms of the individual interest rate swap agreements.

Interest Rate Swaps Designated as Cash Flow Hedges

Forward starting interest rate swaps with notional amounts totaling $20 million and $20 million as of September 30, 2017 and December 31, 2016, respectively, were designated as cash flow hedges of certain liabilities and were determined to be fully effective during all periods presented. As such, no amount of ineffectiveness has been included in net income. Therefore, the aggregate fair value of the swaps is recorded in other assets (liabilities) with changes in fair value recorded in other comprehensive income (loss). The amount included in accumulated other comprehensive income (loss) would be reclassified to current earnings should the hedges no longer be considered effective. The Company expects the hedges to remain fully effective during the remaining terms of the swaps.

Summary information about the interest-rate swaps designated as cash flow hedges was as follows (dollars in thousands):

	September 30, 2017			December 31, 2016
Notional amounts	$	20,000		$	20,000
Weighted average pay rates		3.54	%		3.54	%
Weighted average receive rates	3 month LIBOR			3 month LIBOR
Weighted average maturity	5.7 years			6.5 years
Fair value	$	(1,658	)	$	(1,535	)
Amount of unrealized loss recognized in accumulated other comprehensive income, net of tax	$	(1,023	)	$	(947	)

Pursuant to its interest rate swap agreements, the Company pledged collateral to the counterparties in the form of investment securities with a carrying value of $2.7 million at September 30, 2017. There was no collateral posted from the counterparties to the Company as of September 30, 2017. It is possible that the Company may need to post additional collateral in the future or that the counterparties may be required to post collateral to the Company in the future.

Other Interest Rate Swaps

The Company also enters into swaps to facilitate customer transactions and meet their financing needs. Upon entering into these transactions the Company enters into offsetting positions with large U.S. financial institutions in order to minimize risk to the Company. A summary of the Company’s customer related interest rate swaps was as follows (dollars in thousands):

	September 30, 2017					December 31, 2016
	Notional		Estimated			Notional		Estimated
	amount		fair value			amount		fair value
Interest rate swap agreements:
Pay fixed/receive variable swaps	$	46,021	$	(250	)	$	41,254	$	(460	)
Pay variable/receive fixed swaps		46,021		250			41,254		460
Total	$	92,042	$	—		$	82,508	$	—

Stock Options and Restricted Shares

9 Months Ended

Sep. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Options and Restricted Shares

NOTE 9 – STOCK OPTIONS AND RESTRICTED SHARES

During 2008, the board of directors of the Bank approved the CapStar Bank 2008 Stock Incentive Plan (the Plan). The Plan was intended to provide incentives to certain officers, employees, and directors to stimulate their efforts toward the continued success of the Bank and to operate and manage the business in a manner that will provide for the long‑term growth and profitability of the Bank. Additionally the Plan was intended to encourage stock ownership to align the interests of employees and shareholders and to provide a means of obtaining, rewarding and retaining officers, employees, and directors.

Following the formation of CapStar Financial Holdings, Inc. in 2016, and in connection with the Share Exchange, the outstanding awards of restricted stock and stock options under the CapStar Bank 2008 Stock Incentive Plan were exchanged for similar awards of restricted stock and stock options issued by CapStar Financial Holdings, Inc. under the CapStar Financial Holdings, Inc. Stock Incentive Plan, which the board of directors adopted in 2016. The Stock Incentive Plan provides for the grant of stock-based incentives, including stock options, restricted stock units, performance awards and restricted stock, to employees, directors and service providers that are subject to forfeiture until vesting conditions have been satisfied by the award recipient under the terms of the award. The Plan reserved 1,569,475 shares of stock for issuance of stock incentives. Stock incentives include both restricted share and stock option grants. Total shares issuable under the plan were 169,867 at September 30, 2017.

The Company has recognized stock-based compensation expense, within salaries and employee benefits for employees, and within other non-interest expense for directors, in the consolidated statements of income as follows (dollars in thousands):

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2017			2016			2017			2016
Stock-based compensation expense before income taxes	$	288		$	212		$	771		$	643
Less: deferred tax benefit		(110	)		(81	)		(295	)		(246	)
Reduction of net income	$	178		$	131		$	476		$	397

Restricted Shares

Compensation expense is recognized over the vesting period of the awards based on the fair value of the stock at the issue date. The fair value of each restricted stock grant is based on valuations performed by independent consultants. The recipients have the right to vote and receive dividends but cannot sell, transfer, assign, pledge, hypothecate, or otherwise encumber the restricted stock until the shares have vested. Restricted shares fully vest on the third anniversary of the grant date. A summary of the changes in the Company’s nonvested restricted shares for the nine months ended September 30, 2017 follows:

				Weighted
				Average
	Restricted			Grant Date
Nonvested Shares	Shares			Fair Value
Nonvested at beginning of period		199,641		$	12.34
Granted		37,233			18.05
Vested		(58,921	)		12.24
Forfeited		(3,600	)		13.57
Nonvested at end of period		174,353		$	13.56

As of September 30, 2017, there was $1.6 million of unrecognized compensation cost related to nonvested shares granted under the Plan. The cost is expected to be recognized over a weighted-average period of 1.9 years. The total fair value of shares vested during the nine months ended September 30, 2017 and 2016 was $1.1 million and $0.5 million, respectively.

Stock Options

Option awards are generally granted with an exercise price equal to the fair value of the Company’s common stock at the date of grant. Option awards generally have a three year vesting period and a ten year contractual term.

The fair value of each option grant is estimated on the date of grant using the Black Scholes option pricing model that uses the assumptions noted in the table below. Expected volatility is based on calculations performed by management using industry data. The Company’s expected dividend yield is 0.00% because the Company has not paid dividends in the past. The expected term of options granted was calculated using the “simplified” method for plain vanilla options as permitted under authoritative literature. The risk free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. There were no options granted in 2017.

The fair value of options granted was determined using the following weighted average assumptions as of the grant date:

	2017		2016
Dividend yield		—		—
Expected term (in years)		—		7.48
Expected stock price volatility		—		17.20	%
Risk-free interest rate		—		1.66	%
Pre-vest forfeiture rate		—		10.25	%

A summary of the activity in stock options for the nine months ended September 30, 2017 follows:

						Weighted
				Weighted		Average
				Average		Remaining
				Exercise		Contractual
	Shares			Price		Term (years)
Outstanding at beginning of period		1,006,000		$	10.48
Granted		—			—
Exercised		(82,150	)		10.00
Forfeited or expired		—			—
Outstanding at end of period		923,850		$	10.52		2.5
Fully vested and expected to vest		918,437		$	10.51		2.5
Exercisable at end of period		875,100		$	10.43		2.2

Information related to stock options during each year follows:

	2017		2016
Intrinsic value of options exercised	$	684,275	$	—
Cash received from option exercises		821,500		—
Tax benefit realized from option exercises		263,446		—
Weighted average fair value of options granted		—		3.16

As of September 30, 2017, there was $0.1 million of unrecognized compensation cost related to nonvested stock options granted under the Plan. The cost is expected to be recognized over a weighted-average period of 1.8 years.

Regulatory Capital Requirements

9 Months Ended

Sep. 30, 2017

Banking And Thrift [Abstract]

Regulatory Capital Requirements

NOTE 10 – REGULATORY CAPITAL REQUIREMENTS

The Company and the Bank are subject to regulatory capital requirements administered by the Federal Reserve and the Bank is also subject to the regulatory capital requirements of the Tennessee Department of Financial Institutions. Failure to meet capital requirements can initiate certain mandatory – and possibly additional discretionary – actions by regulators that could, in that event, have a material adverse effect on the institutions’ financial statements. The relevant regulations require the Company and the Bank to meet specific capital adequacy guidelines that involve quantitative measures of their assets, liabilities and certain off-balance-sheet items as calculated under regulatory accounting principles. The capital classifications of the Company and the Bank are also subject to qualitative judgments by their regulators about components, risk weightings, and other factors. Those qualitative judgments could also affect the capital status of the Company and the Bank and the amount of dividends the Company and the Bank may distribute. The final rules implementing the Basel Committee on Banking Supervision’s capital guidelines for U.S. banks (Basel III rules) became effective for the Bank on January 1, 2015 with full compliance with all of the requirements being phased in over a multi-year schedule, and fully phased in by January 1, 2019. The net unrealized gain or loss on available for sale securities is not included in computing regulatory capital. Management believes as of September 30, 2017, the Company and the Bank met all regulatory capital adequacy requirements to which they are subject.

The Company’s and the Bank’s capital amounts and ratios as of September 30, 2017 and December 31, 2016 are presented in the following table (dollars in thousands).

	Actual					Minimum capital requirement (1)					Minimum to be well-capitalized (2)
	Amount		Ratio			Amount		Ratio			Amount		Ratio
At September 30, 2017:
Total capital to risk-weighted assets:
CapStar Financial Holdings, Inc.	$	155,426		12.42	%	$	100,130		8.00	%	N/A		N/A
CapStar Bank		141,843		11.33			100,118		8.00		$	125,147		10.00
Tier I capital to risk-weighted assets:
CapStar Financial Holdings, Inc.		141,125		11.28			75,098		6.00		N/A		N/A
CapStar Bank		127,542		10.19			75,088		6.00			100,118		8.00
Common equity Tier 1 capital to risk weighted assets:
CapStar Financial Holdings, Inc.		132,417		10.58			56,323		4.50		N/A		N/A
CapStar Bank		111,334		8.90			56,316		4.50			81,346		6.50
Tier I capital to average assets:
CapStar Financial Holdings, Inc.		141,125		10.36			54,464		4.00		N/A		N/A
CapStar Bank		127,542		9.37			54,463		4.00			68,079		5.00

At December 31, 2016:
Total capital to risk-weighted assets:
CapStar Financial Holdings, Inc.	$	149,616		12.60	%	$	95,028		8.00	%	N/A		N/A
CapStar Bank		126,718		10.67			95,028		8.00		$	118,785		10.00
Tier I capital to risk-weighted assets:
CapStar Financial Holdings, Inc.		137,909		11.61			71,271		6.00		N/A		N/A
CapStar Bank		115,011		9.68			71,271		6.00			95,028		8.00
Common equity Tier 1 capital to risk weighted assets:
CapStar Financial Holdings, Inc.		129,528		10.90			53,453		4.50		N/A		N/A
CapStar Bank		99,130		8.35			53,453		4.50			77,210		6.50
Tier I capital to average assets:
CapStar Financial Holdings, Inc.		137,909		10.46			52,727		4.00		N/A		N/A
CapStar Bank		115,011		8.72			52,727		4.00			65,909		5.00

(1)

For the calendar year 2017, the Company must maintain a capital conservation buffer of Tier 1 common equity capital in excess of minimum risk-based capital ratios by at least 1.25% to avoid limits on capital distributions and certain discretionary bonus payments to executive officers and similar employees.

(2)

For the Company to be well-capitalized, the Bank must be well-capitalized and the Company must not be subject to any written agreement, order, capital directive, or prompt corrective action directive issued by the Federal Reserve to meet and maintain a specific capital level for any capital measure.

- Definition

The entire disclosure for banks, savings institutions, and credit unions, for regulatory capital requirements imposed by the Federal Reserve System (FRB), the Federal Deposit Insurance Corporation (FDIC), the Office of Thrift Supervision (OTS) or for any state imposed capital requirements, as applicable. The disclosure may include (1) a description of regulatory capital requirements (a) for capital adequacy purposes and (b) established by the prompt corrective action provisions of Section 38 of the Federal Depository Insurance Act; (2) the actual or possible material effects of noncompliance with such requirements; (3) whether the entity is in compliance with the regulatory capital requirements including (a) required and actual ratios and amounts of Tier 1 leverage, Tier 1 risk-based, and total risk-based capital, tangible capital (for savings institutions), and Tier 3 capital for market risk (for certain banks and bank holding companies), (b) factors that may significantly affect capital adequacy; (4) the prompt corrective action category in which the entity was classified as of its most recent notification; (5) whether management believes any conditions or events since notification have changed the entity's category. Also may include additional information that might be disclosed in situations where substantial doubt about the entity's ability to continue as a going concern for a reasonable period of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1G
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958577-112826

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1C
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958572-112826

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1E
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958574-112826

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958569-112826

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958570-112826

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1F
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958575-112826

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1D
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958573-112826

+ Details

Earnings Per Share

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Earnings Per Share

NOTE 11 – EARNINGS PER SHARE

The following is a summary of the basic and diluted earnings per share calculation for the three and nine months ended September 30, 2017 and 2016 (dollars in thousands, except share data):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2017		2016		2017		2016
Basic net income per share calculation:
Numerator – Net income	$	4,419	$	2,109	$	1,409	$	6,169
Denominator – Average common shares outstanding		11,279,364		8,792,665		11,239,093		8,701,596
Basic net income per share	$	0.39	$	0.24	$	0.13	$	0.71
Diluted net income per share calculation:
Numerator – Net income	$	4,419	$	2,109	$	1,409	$	6,169
Denominator – Average common shares outstanding		11,279,364		8,792,665		11,239,093		8,701,596
Dilutive shares contingently issuable		1,471,059		2,006,871		1,518,998		1,981,380
Average diluted common shares outstanding		12,750,423		10,799,536		12,758,091		10,682,976
Diluted net income per share	$	0.35	$	0.20	$	0.11	$	0.58

Fair Value

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Fair Value

NOTE 12 – FAIR VALUE

Fair value is the exchange price that would be received for an asset or paid to transfer a liability (exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There are three levels of inputs that may be used to measure fair values:

Level 1:

Quoted prices (unadjusted) for identical assets or liabilities in active markets that the entity has the ability to access as of the measurement date.

Level 2:

Significant observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data.

Level 3:

Significant unobservable inputs that reflect a reporting entity’s own assumptions about the assumptions that market participants would use in pricing an asset or liability.

The Bank used the following methods and significant assumptions to estimate fair value:

Investment Securities: The fair values for investment securities are determined by quoted market prices, if available (Level 1). For securities where quoted prices are not available, fair values are calculated based on market prices of similar securities (Level 2), using matrix pricing. Matrix pricing is a mathematical technique commonly used to price debt securities that are not actively traded and, values debt securities by relying on quoted prices for the specific securities and the securities’ relationship to other benchmark quoted securities (Level 2 inputs). For securities where quoted prices or market prices of similar securities are not available, fair values are calculated using discounted cash flows or other market indicators (Level 3). See below for additional discussion of Level 3 valuation methodologies and significant inputs. The fair values of all securities are determined from third party pricing services without adjustment.

Derivatives-Interest Rate Swaps: The fair values of derivatives are based on valuation models using observable market data as of the measurement date (Level 2). The Bank’s derivatives are traded in an over-the-counter market where quoted market prices are not always available. Therefore, the fair values of derivatives are determined using quantitative models that utilize multiple market inputs. The inputs will vary based on the type of derivative, but could include interest rates, prices and indices to generate continuous yield or pricing curves, prepayment rates, and volatility factors to value the position. The majority of market inputs are actively quoted and can be validated through external sources, including brokers, market transactions and third-party pricing services. The fair values of all interest rate swaps are determined from third party pricing services without adjustment.

Impaired Loans: The fair value of impaired loans with specific allocations of the allowance for loan losses is generally based on recent appraisals. These appraisals may utilize a single valuation approach or a combination of approaches including comparable sales and the income approach. Adjustments are routinely made in the appraisal process by the independent appraisers to adjust for differences between the comparable sales and income data available for similar loans and collateral underlying such loans. Such adjustments result in a Level 3 classification of the inputs for determining fair value. Collateral may be valued using an appraisal, net book value per the borrower’s financial statements, or aging reports, adjusted or discounted based on management’s historical knowledge, changes in market conditions from the time of the valuation, and management’s expertise and knowledge of the client and client’s business, resulting in a Level 3 fair value classification. Impaired loans are evaluated on at least a quarterly basis for additional impairment and adjusted in accordance with the loan policy.

Other Real Estate Owned: Assets acquired through or instead of loan foreclosure are initially recorded at fair value less costs to sell when acquired, establishing a new cost basis. These assets are subsequently accounted for at lower of cost or fair value less estimated costs to sell. Fair value is commonly based on recent real estate appraisals which are updated no less frequently than annually. These appraisals may utilize a single valuation approach or a combination of approaches including comparable sales and the income approach with data from comparable properties. Adjustments are routinely made in the appraisal process by the independent appraisers to adjust for differences between the comparable sales and income data available. Appraisals may be adjusted or discounted based on management’s historical knowledge, changes in market conditions from the time of the valuation, and/or management’s expertise and knowledge of the collateral. Such adjustments result in a Level 3 classification of the inputs for determining fair value. Real estate owned properties are evaluated on a quarterly basis for additional impairment and adjusted accordingly. The Company had no other real estate owned at September 30, 2017 or December 31, 2016.

Loans Held For Sale: Loans held for sale are carried at the lower of cost or fair value, which is evaluated on a pool-level basis. The fair value of loans held for sale is determined using quoted prices for similar assets, adjusted for specific attributes of that loan or other observable market data, such as outstanding commitments from third party investors (Level 2). There were no loans held for sale carried at fair value at September 30, 2017 or December 31, 2016.

Assets and liabilities measured at fair value on a recurring basis are summarized below (dollars in thousands):

	Fair value measurements at September 30, 2017
				Quoted prices
				in active		Significant
				markets for		other			Significant
				identical		observable			unobservable
	Carrying			assets		inputs			inputs
	Value			(Level 1)		(Level 2)			(Level 3)
Assets:
Securities available for sale:
U.S. government-sponsored agencies	$	11,299		$	—	$	11,299		$	—
Obligations of states and political subdivisions		19,067			—		19,067			—
Mortgage-backed securities-residential		95,823			—		95,823			—
Asset-backed securities		20,411			—		20,411			—
Total securities available for sale	$	146,600		$	—	$	146,600		$	—
Derivatives:
Interest rate swaps - customer related	$	352		$	—	$	352		$	—
Liabilities:
Derivatives:
Interest rate swaps - customer related	$	(352	)	$	—	$	(352	)	$	—
Interest rate swaps - cash flow hedges		(1,658	)		—		(1,658	)		—
Total derivatives	$	(2,010	)	$	—	$	(2,010	)	$	—

	Fair value measurements at December 31, 2016
				Quoted prices
				in active		Significant
				markets for		other			Significant
				identical		observable			unobservable
	Carrying			assets		inputs			inputs
	Value			(Level 1)		(Level 2)			(Level 3)
Assets:
Securities available for sale:
U.S. government-sponsored agencies	$	9,374		$	—	$	9,374		$	—
Obligations of states and political subdivisions		27,913			—		27,913			—
Mortgage-backed securities-residential		124,595			—		124,595			—
Asset-backed securities		20,473			—		20,473			—
Total securities available for sale	$	182,355		$	—	$	182,355		$	—
Derivatives:
Interest rate swaps - customer related	$	460		$	—	$	460		$	—
Liabilities:
Derivatives:
Interest rate swaps - customer related	$	(460	)	$	—	$	(460	)	$	—
Interest rate swaps - cash flow hedges		(1,535	)		—		(1,535	)		—
Total derivatives	$	(1,995	)	$	—	$	(1,995	)	$	—

Assets measured at fair value on a nonrecurring basis are summarized below (dollars in thousands):

Fair value measurements at September 30, 2017

Quoted prices

in active

Significant

markets for

other

Significant

identical

observable

unobservable

Carrying

assets

inputs

Value

(level 1)

(level 2)

(level 3)

Assets:

Impaired loans:

Commercial and industrial

1,432

—

1,432

Fair value measurements at December 31, 2016

Quoted prices

in active

Significant

markets for

other

Significant

identical

observable

unobservable

Carrying

assets

inputs

Value

(level 1)

(level 2)

(level 3)

Assets:

Impaired loans:

Commercial and industrial

1,809

—

1,809

The following table presents quantitative information about Level 3 fair value measurements for assets measured at fair value on a non-recurring basis at September 30, 2017 and December 31, 2016 (dollars in thousands):

Range

Fair

Valuation

(Weighted-

September 30, 2017

Value

Technique(s)

Unobservable Input(s)

Average)

Impaired loans:

Commercial and industrial

1,432

Sales comparison approach

Appraisal discounts

Range

Fair

Valuation

(Weighted-

December 31, 2016

Value

Technique(s)

Unobservable Input(s)

Average)

Impaired loans:

Commercial and industrial

1,809

Sales comparison approach

Appraisal discounts

Fair Value of Financial Instruments

The carrying value and estimated fair values of the Bank’s financial instruments at September 30, 2017 and December 31, 2016 were as follows (dollars in thousands):

	September 30, 2017				December 31, 2016
	Carrying				Carrying				Fair value
	amount		Fair value		amount		Fair value		level of input
Financial assets:
Cash and due from banks, interest-bearing deposits in financial institutions	$	69,789	$	69,789	$	63,456	$	63,456	Level 1
Federal funds sold		—		—		16,654		16,654	Level 1
Securities available for sale		146,600		146,600		182,355		182,355	Level 2
Securities held to maturity		45,635		48,980		46,864		49,731	Level 2
Loans held for sale		53,225		54,407		42,111		42,302	Level 2
Restricted equity securities		8,799	N/A			6,032	N/A		N/A
Loans, net of unearned income		974,530		974,551		935,251		934,628	Level 3
Accrued interest receivable		3,849		3,849		3,942		3,942	Level 2
Bank owned life insurance		22,335		22,335		21,900		21,900	Level 2
Other assets		352		352		460		460	Level 2
Financial liabilities:
Deposits		1,091,495		1,050,801		1,128,723		1,088,758	Level 3
Federal Home Loan Bank advances		95,000		94,980		55,000		54,989	Level 2
Accrued interest payable		305		305		212		212	Level 2
Other liabilities		3,800		3,800		5,349		5,349	Level 3

The methods and assumptions, not previously presented, used to estimate fair values are described as follows:

(a)	Cash and Due from Banks, Interest-Bearing Deposits in Financial Institutions

For these short‑term instruments, the carrying amount is a reasonable estimate of fair value.

(b)	Federal Funds Sold

Federal funds sold clear on a daily basis. For this reason, the carrying amount is a reasonable estimate of fair value.

(c)	Restricted Equity Securities

It is not practical to determine the fair value of restricted securities due to restrictions placed on their transferability.

(d)	Loans, net

The fair value of the Bank’s loan portfolio includes a credit risk assumption in the determination of the fair value of its loans. This credit risk assumption is intended to approximate the fair value that a market participant would realize in a hypothetical orderly transaction. The Bank’s loan portfolio is initially fair valued using a segmented approach. The Bank divides its loan portfolio into the following categories: variable rate loans, impaired loans and all other loans. The results are then adjusted to account for credit risk. For variable‑rate loans that reprice frequently and have no significant change in credit risk, fair values approximate carrying values. Fair values for impaired loans are estimated using discounted cash flow models or based on the fair value of the underlying collateral. For other loans, fair values are estimated using discounted cash flow models, using current market interest rates offered for loans with similar terms to borrowers of similar credit quality. The values derived from the discounted cash flow approach for each of the above portfolios are then further discounted to incorporate credit risk. The methods utilized to estimate the fair value of loans do not necessarily represent an exit price.

(e)	Bank Owned Life Insurance

For bank owned life insurance, the carrying amount is based on the cash surrender value and is a reasonable estimate of fair value.

(f)	Other Assets

Included in other assets are certain interest rate swap agreements and the cash flow hedge relationships. The fair values of interest rate swap agreements and the cash flow hedge relationships are based on independent pricing services that utilize pricing models with observable market inputs.

(g)

Deposits

The fair value of demand deposits, savings accounts and certain money market deposits is the amount payable on demand at the reporting date. The fair value of certificates of deposit is estimated by discounted cash flow models, using current market interest rates offered on certificates with similar remaining maturities.

(h)	Federal Home Loan Bank Advances

The fair value of fixed rate Federal Home Loan Bank Advances is estimated using discounted cash flow models, using current market interest rates offered on certificates, advances and other borrowings with similar remaining maturities.

(i)	Accrued Interest Receivable/Payable

The carrying amounts of accrued interest approximate fair value.

(j)	Other Liabilities

Included in other liabilities are certain interest rate swap agreements, the cash flow hedge relationships and contingent consideration. The fair values of interest rate swap agreements and the cash flow hedge relationships are based on independent pricing services that utilize pricing models with observable market inputs. The fair value of contingent consideration is estimated by a discounted cash flow model that utilizes various unobservable inputs.

(k)	Off-Balance Sheet Instruments

Fair values for off-balance sheet, credit-related financial instruments are based on fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreements and the counterparties’ credit standing. The fair value of commitments is not material.

(l)	Limitations

Fair value estimates are made at a specific point in time, based on relevant market information and information about the financial instruments. These estimates do not reflect any premium or discount that could result from offering for sale at one time the Bank’s entire holdings of a particular instrument. Because no market exists for a significant portion of the Bank’s financial instruments, fair value estimates are based on judgments regarding future expected loss experience, current economic conditions, risk characteristics of various financial instruments, and other factors. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and, therefore, cannot be determined with precision. Changes in assumptions could significantly affect the estimates.

Fair value estimates are based on estimating on and off‑balance sheet financial instruments without attempting to estimate the value of anticipated future business and the value of assets and liabilities that are not considered financial instruments. For example, fixed assets are not considered financial instruments and their value has not been incorporated into the fair value estimates. In addition, the tax ramifications related to the realization of the unrealized gains and losses can have a significant effect on fair value estimates and have not been considered in the estimates.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements as of and for the period ended September 30, 2017 include CapStar Financial Holdings, Inc. and its wholly owned subsidiary, CapStar Bank (the “Bank”, together referred to as the “Company”). Significant intercompany transactions and accounts are eliminated in consolidation. On February 5, 2016, CapStar Financial Holdings, Inc. acquired all of the Bank’s issued and outstanding shares of common stock, preferred stock, common stock options and warrants, and the Bank became the wholly owned subsidiary of CapStar Financial Holdings, Inc. The accompanying unaudited consolidated financial statements have been prepared in accordance with instructions to Form 10-Q and do not include all information and footnotes required by U.S. generally accepted accounting principles (“U.S. GAAP”) for complete financial statements. All adjustments consisting of normally recurring accruals that, in the opinion of management, are necessary for a fair presentation of the financial position and results of operations for the periods presented have been included. These unaudited consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements and related notes appearing in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016.
Initial Public Offering	Initial Public Offering On September 21, 2016, the Securities and Exchange Commission (“SEC”) declared effective our registration statement on Form S-1 registering the shares of our common stock. On September 27, 2016, we completed the initial public offering of 2,972,750 shares of our common stock. Of the 2,972,750 shares sold, 1,688,049 shares were sold by us and 1,284,701 shares were sold by certain selling shareholders. Of the 1,284,701 shares sold by certain selling shareholders, 731,707 were from preferred shares converted to common shares and 79,166 from the cashless exercise of 250,000 common share warrants. We received net proceeds of approximately $21.9 million from the offering, after deducting the underwriting discounts and commissions and estimated offering expenses. We did not receive any proceeds from the sale of shares by the selling shareholders.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Material estimates that are particularly susceptible to significant change relate to the determination of the allowance for loan losses, determination of impairment of intangible assets, including goodwill, the valuation of our investment portfolio, deferred tax assets and estimated liabilities. There have been no significant changes to the Company’s critical accounting policies as disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016.
Tri-Net Fees	Tri-Net Fees Tri-Net fees represent a new line of business, implemented in the fourth quarter of 2016, which originates, with the intent to sell, commercial real estate loans to third-party investors. All of these loan sales transfer servicing rights to the buyer. Realized gains and losses are recognized when legal title of the loan has transferred to the investor and sales proceeds have been received and are reflected in the accompanying statement of income in Tri-Net fees, net of related costs such as commission expenses. Loans that have not been sold at period end are classified as held for sale on the balance sheet and recorded at the lower of aggregate cost or fair value. Net unrealized losses, if any, are recorded as a valuation allowance and charged to earnings.
Subsequent Events	Subsequent Events Accounting Standards Codification (“ASC”) 855, Subsequent Events, establishes general standards of accounting for and disclosure of events that occur after the balance sheet date but before financial statements are issued. The Company evaluated all events or transactions that occurred after September 30, 2017 through the date of the issued financial statements.

Securities (Tables)

9 Months Ended

Sep. 30, 2017

Investments Debt And Equity Securities [Abstract]

Summary of Amortized Cost and Fair Value of Available-for-sale and Held-to-maturity Securities

The amortized cost and fair value of securities available-for-sale and held-to-maturity at September 30, 2017 and December 31, 2016 are summarized as follows (dollars in thousands):

	September 30, 2017									December 31, 2016
	Amortized Cost		Gross unrealized gains		Gross unrealized (losses)			Estimated fair value		Amortized Cost		Gross unrealized gains		Gross unrealized (losses)			Estimated fair value
Securities available-for-sale:
U. S. government agency securities	$	11,434	$	18	$	(153	)	$	11,299	$	9,517	$	—	$	(143	)	$	9,374
State and municipal securities		19,031		172		(136	)		19,067		28,480		65		(632	)		27,913
Mortgage-backed securities		96,975		14		(1,166	)		95,823		126,637		17		(2,059	)		124,595
Asset-backed securities		20,668		—		(257	)		20,411		21,620		—		(1,147	)		20,473
Total	$	148,108	$	204	$	(1,712	)	$	146,600	$	186,254	$	82	$	(3,981	)	$	182,355
Securities held-to-maturity:
State and municipal securities	$	36,469	$	3,138	$	—		$	39,607	$	36,842	$	2,784	$	—		$	39,626
Mortgage-backed securities		3,837		77		—			3,914		4,687		79		—			4,766
Other debt securities		5,329		130		—			5,459		5,335		11		(7	)		5,339
Total	$	45,635	$	3,345	$	—		$	48,980	$	46,864	$	2,874	$	(7	)	$	49,731

Summary of Securities with Unrealized Losses and Length of Time Continuous Loss Positions

	Less than 12 months					12 months or more					Total
September 30, 2017	Estimated fair value		Gross unrealized losses			Estimated fair value		Gross unrealized losses			Estimated fair value		Gross unrealized losses
U. S. government agency securities	$	9,303	$	(153	)	$	—	$	—		$	9,303	$	(153	)
State and municipal securities		4,968		(19	)		6,103		(117	)		11,071		(136	)
Mortgage-backed securities		61,997		(591	)		30,360		(575	)		92,357		(1,166	)
Asset-backed securities		—		—			20,410		(257	)		20,410		(257	)
Total temporarily impaired securities	$	76,268	$	(763	)	$	56,873	$	(949	)	$	133,141	$	(1,712	)

December 31, 2016
U. S. government agency securities	$	9,374	$	(143	)	$	—	$	—		$	9,374	$	(143	)
State and municipal securities		20,279		(632	)		—		—			20,279		(632	)
Mortgage-backed securities		110,563		(1,955	)		4,150		(104	)		114,713		(2,059	)
Asset-backed securities		—		—			20,473		(1,147	)		20,473		(1,147	)
Other debt securities		2,029		(7	)		—		—			2,029		(7	)
Total temporarily impaired securities	$	142,245	$	(2,737	)	$	24,623	$	(1,251	)	$	166,868	$	(3,988	)

Summary of Proceeds from Sales of Securities and Associated Gains and Losses

The proceeds from sales of securities and the associated gains and losses are listed below (dollars in thousands):

	Nine Months Ended			Nine Months Ended
	September 30, 2017			September 30, 2016
Proceeds	$	34,299		$	46,700
Gross gains		99			244
Gross losses		(57	)		(123	)

Summary of Amortized Cost and Fair Value of Debt Securities by Contractual Maturity

	Available-for-sale				Held-to-maturity
	Amortized cost		Estimated fair value		Amortized cost		Estimated fair value
Due one to five years	$	11,388	$	11,511	$	27,299	$	29,448
Due five to ten years		17,970		17,788		14,069		15,129
Due beyond ten years		1,107		1,067		430		489
Mortgage-backed securities		96,975		95,823		3,837		3,914
Asset-backed securities		20,668		20,411		—		—
	$	148,108	$	146,600	$	45,635	$	48,980

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Loans and Allowance for Loan Losses (Tables)

9 Months Ended

Sep. 30, 2017

Receivables [Abstract]

Summary of Loan Portfolio

A summary of the loan portfolio as of September 30, 2017 and December 31, 2016 follows (dollars in thousands):

	September 30, 2017			December 31, 2016
Commercial real estate	$	366,778		$	302,322
Consumer real estate		100,811			97,015
Construction and land development		79,951			94,491
Commercial and industrial		394,600			379,620
Consumer		6,289			5,974
Other		26,460			56,796
Total		974,889			936,218
Less net unearned income		(359	)		(967	)
		974,530			935,251
Allowance for loan losses		(14,122	)		(11,634	)
	$	960,408		$	923,617

Summary of Loans by Risk Rating

The following tables present the loan balances by category as well as risk rating (dollars in thousands):

	Performing Loans
September 30, 2017	Pass/Watch		Special Mention		Substandard		Total Performing		Total Impaired Loans		Total
Commercial real estate	$	365,545	$	—	$	—	$	365,545	$	1,233	$	366,778
Consumer real estate		100,522		—		289		100,811		—		100,811
Construction and land development		79,951		—		—		79,951		—		79,951
Commercial and industrial		370,657		16,443		5,568		392,668		1,932		394,600
Consumer		6,276		—		13		6,289		—		6,289
Other		26,460		—		—		26,460		—		26,460
Total	$	949,411	$	16,443	$	5,870	$	971,724	$	3,165	$	974,889

December 31, 2016
Commercial real estate	$	301,012	$	—	$	—	$	301,012	$	1,310	$	302,322
Consumer real estate		96,722		—		293		97,015		—		97,015
Construction and land development		94,491		—		—		94,491		—		94,491
Commercial and industrial		349,857		11,035		16,419		377,311		2,309		379,620
Consumer		5,958		—		16		5,974		—		5,974
Other		56,796		—		—		56,796		—		56,796
Total	$	904,836	$	11,035	$	16,728	$	932,599	$	3,619	$	936,218

Summary of Changes and Breakdown of Allowance for Loan Losses and Loan Portfolio by Loan Category

The following tables detail the changes in the ALL for the three and nine months ended September 30, 2017 and 2016 (in thousands):

	Commercial real estate			Consumer real estate			Construction and land development		Commercial and industrial			Consumer			Other			Total
Three Months Ended September 30, 2017
Balance, beginning of period	$	3,533		$	1,081		$	911	$	6,395		$	57		$	477		$	12,454
Charged-off loans		—			—			—		—			—			—			—
Recoveries		3			—			—		1,860			—			—			1,863
Provision for loan losses		(242	)		(97	)		576		(306	)		22			(148	)		(195	)
Balance, end of period	$	3,294		$	984		$	1,487	$	7,949		$	79		$	329		$	14,122

Three Months Ended September 30, 2016
Balance, beginning of period	$	2,596		$	968		$	943	$	5,037		$	104		$	806		$	10,454
Charged-off loans		—			—			—		(645	)		—						(645	)
Recoveries		52			—			—		10			—			—			62
Provision for loan losses		(228	)		4			721		1,166			(18	)		(6	)		1,639
Balance, end of period	$	2,420		$	972		$	1,664	$	5,568		$	86		$	800		$	11,510

	Commercial real estate			Consumer real estate			Construction and land development			Commercial and industrial			Consumer			Other			Total
Nine Months Ended September 30, 2017
Balance, beginning of period	$	2,655		$	1,013		$	1,574		$	5,618		$	76		$	698		$	11,634
Charged-off loans		—			—			—			(12,369	)		—			—			(12,369	)
Recoveries		4			—			—			1,862			91			—			1,957
Provision for loan losses		635			(29	)		(87	)		12,838			(88	)		(369	)		12,900
Balance, end of period	$	3,294		$	984		$	1,487		$	7,949		$	79		$	329		$	14,122

Nine Months Ended September 30, 2016
Balance, beginning of period	$	2,879		$	968		$	914		$	4,693		$	103		$	575		$	10,132
Charged-off loans		(350	)		—			—			(956	)		(146	)		—			(1,452	)
Recoveries		52			—			—			18			1			—			71
Provision for loan losses		(161	)		4			750			1,813			128			225			2,759
Balance, end of period	$	2,420		$	972		$	1,664		$	5,568		$	86		$	800		$	11,510

A breakdown of the ALL and the loan portfolio by loan category at September 30, 2017 and December 31, 2016 follows (dollars in thousands):

	Commercial real estate		Consumer real estate		Construction and land development		Commercial and industrial		Consumer		Other		Total
September 30, 2017
Allowance for Loan Losses:
Collectively evaluated for impairment	$	3,294	$	984	$	1,487	$	7,449	$	79	$	329	$	13,622
Individually evaluated for impairment		—		—		—		500		—		—		500
Balances, end of period	$	3,294	$	984	$	1,487	$	7,949	$	79	$	329	$	14,122
Loans:
Collectively evaluated for impairment	$	365,545	$	100,811	$	79,951	$	392,668	$	6,289	$	26,460	$	971,724
Individually evaluated for impairment		1,233		—		—		1,932		—		—		3,165
Balances, end of period	$	366,778	$	100,811	$	79,951	$	394,600	$	6,289	$	26,460	$	974,889

December 31, 2016
Allowance for Loan Losses:
Collectively evaluated for impairment	$	2,655	$	1,013	$	1,574	$	5,118	$	76	$	698	$	11,134
Individually evaluated for impairment		—		—		—		500		—		—		500
Balances, end of period	$	2,655	$	1,013	$	1,574	$	5,618	$	76	$	698	$	11,634
Loans:
Collectively evaluated for impairment	$	301,012	$	97,015	$	94,491	$	377,311	$	5,974	$	56,796	$	932,599
Individually evaluated for impairment		1,310		—		—		2,309		—		—		3,619
Balances, end of period	$	302,322	$	97,015	$	94,491	$	379,620	$	5,974	$	56,796	$	936,218

Allocation of ALL with Corresponding Percentage of ALL in Each Category to Total Loans, Net of Deferred Fee

	September 30, 2017					December 31, 2016
	Amount		Percent of total loans, net of deferred fees			Amount		Percent of total loans, net of deferred fees
Commercial real estate	$	3,294		0.34	%	$	2,655		0.28	%
Consumer real estate		984		0.10			1,013		0.11
Construction and land development		1,487		0.15			1,574		0.17
Commercial and industrial		7,949		0.82			5,618		0.60
Consumer		79		0.01			76		0.01
Other		329		0.03			698		0.07
Total allowance for loan losses	$	14,122		1.45	%	$	11,634		1.24	%

Summary of Impaired Loans

The following table presents the Company’s impaired loans that were evaluated for specific loss allowance as of September 30, 2017 and December 31, 2016 (dollars in thousands):


	September 30, 2017						December 31, 2016
	Recorded investment		Unpaid principal balance		Related allowance		Recorded investment		Unpaid principal balance		Related allowance
With no related allowance recorded:
Commercial real estate	$	1,233	$	1,660	$	—	$	1,310	$	1,686	$	—
Consumer real estate		—		—		—		—		—		—
Construction and land development		—		—		—		—		—		—
Commercial and industrial		—		—		—		—		—		—
Consumer		—		—		—		—		—		—
Other		—		—		—		—		—		—
Subtotal		1,233		1,660		—		1,310		1,686		—
With an allowance recorded:
Commercial real estate		—		—		—		—		—		—
Consumer real estate		—		—		—		—		—		—
Construction and land development		—		—		—		—		—		—
Commercial and industrial		1,932		2,770		500		2,309		2,921		500
Consumer		—		—		—		—		—		—
Other		—		—		—		—		—		—
Subtotal		1,932		2,770		500		2,309		2,921		500
Total	$	3,165	$	4,430	$	500	$	3,619	$	4,607	$	500

	Three Months Ended				Three Months Ended				Nine Months Ended				Nine Months Ended
	September 30, 2017				September 30, 2016				September 30, 2017				September 30, 2016
	Average recorded investment		Interest income recognized		Average recorded investment		Interest income recognized		Average recorded investment		Interest income recognized		Average recorded investment		Interest income recognized
With no related allowance recorded:
Commercial real estate	$	1,245	$	—	$	—	$	—	$	1,272	$	—	$	—	$	—
Consumer real estate		—		—		—		—		—		—		—		—
Construction and land development		—		—		—		—		—		—		—		—
Commercial and industrial		—		—		—		—		—		—		—		—
Consumer		—		—		—		—		—		—		—		—
Other		—		—		—		—		—		—		—		—
Subtotal		1,245		—		—		—		1,272		—		—		—
With an allowance recorded:
Commercial real estate		—		—		1,685		—		—		—		1,742		—
Consumer real estate		—		—		—		—		—		—		—		—
Construction and land development		—		—		—		—		—		—		—		—
Commercial and industrial		1,941		—		3,411		—		2,141		—		3,534		30
Consumer		—		—		—		—		—		—		—		—
Other		—		—		—		—		—		—		—		—
Subtotal		1,941		—		5,096		—		2,141		—		5,276		30
Total	$	3,186	$	—	$	5,096	$	—	$	3,413	$	—	$	5,276	$	30

Schedule of Aging of Recorded Investment in Past-due Loans, by Class of Loans

The following table presents the aging of the recorded investment in past-due loans as of September 30, 2017 and December 31, 2016 by class of loans (dollars in thousands):

	30 - 59		60 - 89		Greater Than
	Days		Days		89 Days		Total		Loans Not
	Past Due		Past Due		Past Due		Past Due		Past Due		Total
September 30, 2017
Commercial real estate	$	—	$	—	$	—	$	—	$	366,778	$	366,778
Consumer real estate		506		279		—		785		100,026		100,811
Construction and land development		—		—		—		—		79,951		79,951
Commercial and industrial		1,154		218		27		1,398		393,202		394,600
Consumer		—		1		—		1		6,288		6,289
Other		—		—		—		—		26,460		26,460
Total	$	1,660	$	497	$	27	$	2,184	$	972,705	$	974,889

December 31, 2016
Commercial real estate	$	—	$	—	$	—	$	—	$	302,322	$	302,322
Consumer real estate		81		282		—		363		96,652		97,015
Construction and land development		—		—		—		—		94,491		94,491
Commercial and industrial		—		—		—		—		379,620		379,620
Consumer		—		—		—		—		5,974		5,974
Other		—		—		—		—		56,796		56,796
Total	$	81	$	282	$	—	$	363	$	935,855	$	936,218

Schedule of Recorded In Non Accrual Loans, Past Due Loans over 90 Days Outstanding and Accruing and Troubled Debt Restructurings

	Non-Accrual		Past Due Over 90 Days and Accruing		Troubled Debt Restructurings
September 30, 2017
Commercial real estate	$	1,233	$	—	$	1,222
Consumer real estate		—		—		—
Construction and land development		—		—		—
Commercial and industrial		1,932		27		—
Consumer		—		—		—
Other		—		—		—
Total	$	3,165	$	27	$	1,222

December 31, 2016
Commercial real estate	$	1,310	$	—	$	1,272
Consumer real estate		—		—		—
Construction and land development		—		—		—
Commercial and industrial		2,309		—		—
Consumer		—		—		—
Other		—		—		—
Total	$	3,619	$	—	$	1,272

Schedule of Presents Loans by Class Modified as TDR

The following table presents loans by class modified as TDR that occurred during the three and nine months ended September 30, 2016 (dollars in thousands).

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	Number of contracts		Pre modification outstanding recorded investment		Post modification outstanding recorded investment, net of related allowance		Number of contracts		Pre modification outstanding recorded investment		Post modification outstanding recorded investment, net of related allowance
2016
Commercial real estate		—	$	—	$	—		1	$	1,948	$	1,170
Consumer real estate		—		—		—		—		—		—
Construction and land development		—		—		—		—		—		—
Commercial and industrial		—		—		—		—		—		—
Consumer		—		—		—		—		—		—
Other		—		—		—		—		—		—
Total		—	$	—	$	—		1	$	1,948	$	1,170

Schedule of Loans by Class Modified as TDR for the Payment Default Within Twelve Months

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	Number of contracts		Recorded investment		Number of contracts		Recorded investment
2016
Commercial real estate		—	$	—		—	$	—
Consumer real estate		—		—		—		—
Construction and land development		—		—		—		—
Commercial and industrial		—		—		—		—
Consumer		—		—		1		124
Other		—		—		—		—
Total		—	$	—		1	$	124

Federal Home Loan Bank Advances (Tables)

9 Months Ended

Sep. 30, 2017

Federal Home Loan Banks [Abstract]

Summary of Contractual Maturities and Average Effective Rates of Outstanding Advances

The following is a summary of the contractual maturities and average effective rates of outstanding advances (dollars in thousands):

	September 30, 2017					December 31, 2016
Year	Amount		Interest Rates			Amount		Interest Rates
2017	$	60,000		1.18	%	$	55,000		0.80	%
2018		35,000		1.50			—		—
2019		—		—			—		—
2020		—		—			—		—
2021		—		—			—		—
Thereafter		—		—			—		—
Total	$	95,000		1.30	%	$	55,000		0.80	%

Accumulated Other Comprehensive Income (Loss) (Tables)

9 Months Ended

Sep. 30, 2017

Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]

Summary of Changes in Accumulated Other Comprehensive Income (Loss) by Component, Net of Tax

The following were changes in accumulated other comprehensive income (loss) by component, net of tax, for the nine months ended September 30, 2017 and 2016 (dollars in thousands):

				Unrealized Gains			Unrealized
	Gains and			and Losses			Losses on
	Losses on			on Available			Securities
	Cash Flow			for Sale			Transferred to
	Hedges			Securities			Held to Maturity			Total
Nine Months Ended September 30, 2017
Beginning Balance	$	(4,241	)	$	(698	)	$	(1,212	)	$	(6,151	)
Other comprehensive income (loss) before reclassification, net of tax		(193	)		1,502			—			1,309
Amounts reclassified from accumulated other comprehensive income (loss), net of tax		589			(26	)		100			663
Net current period other comprehensive income (loss)		396			1,476			100			1,972
Ending Balance	$	(3,845	)	$	778		$	(1,112	)	$	(4,179	)

Nine Months Ended September 30, 2016
Beginning Balance	$	(3,704	)	$	105		$	(1,315	)	$	(4,914	)
Other comprehensive income (loss) before reclassification, net of tax		(1,086	)		1,746			—			660
Amounts reclassified from accumulated other comprehensive income (loss), net of tax		261			(75	)		77			263
Net current period other comprehensive income (loss)		(825	)		1,671			77			923
Ending Balance	$	(4,529	)	$	1,776		$	(1,238	)	$	(3,991	)

Summary of Significant Amounts Reclassified out off Accumulated Other Comprehensive Income (Loss)

													Affected Line Item
Details about Accumulated Other	Three Months Ended September 30,						Nine Months Ended September 30,						in the Statement Where
Comprehensive Income Components	2017			2016			2017			2016			Net Income is Presented
Unrealized losses on cash flow hedges	$	109		$	38		$	322		$	113		Interest expense - money market
		168			50			267			148		Interest expense - Federal Home Loan Bank advances
	$	277		$	88		$	589		$	261		Net of tax
Unrealized (gains) and losses on available for sale securities	$	(9	)	$	4		$	(42	)	$	(121	)	Net (gain) loss on sale of securities
		3			(2	)		16			46		Income tax expense (benefit)
	$	(6	)	$	2		$	(26	)	$	(75	)	Net of tax
Unrealized losses on securities transferred to held to maturity	$	79		$	42		$	162		$	125		Interest income - securities
		(30	)		(16	)		(62	)		(48	)	Income tax benefit
	$	49		$	26		$	100		$	77		Net of tax

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2017

Commitments And Contingencies Disclosure [Abstract]

Schedule of Financial Instruments Representing Credit Risk

The following table sets forth outstanding financial instruments whose contract amounts represent credit risk as of September 30, 2017 and December 31, 2016 (dollars in thousands):

	Contract or notional amount
	September 30, 2017		December 31, 2016
Financial instruments whose contract amounts represent credit risk:
Unused commitments to extend credit	$	575,558	$	508,990
Standby letters of credit		11,535		10,886
Total	$	587,093	$	519,876

- Definition

Tabular disclosure of all significant concentrations of risk, including credit risk and market risk, arising from all financial instruments (as defined), whether from an individual counterparty or groups of counterparties. The disclosure concerning concentrations of risk may consist of the following information: (1) for concentrations of credit risk disclosure may include: (a) information about the (shared) activity, region, or economic characteristic that identifies the concentration, (b) the maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity, (c) the policy of requiring collateral or other security to support financial instruments subject to credit risk, information about the entity's access to that collateral or other security, and the nature and a brief description of the collateral or other security supporting those financial instruments, and (d) the policy of entering into master netting arrangements to mitigate the credit risk of financial instruments, information about the arrangements for which the entity is a party, and a brief description of the terms of those arrangements, including the extent to which they would reduce the entity's maximum amount of loss due to credit risk and (2) for disclosure of quantitative information about the market risks of financial instruments that is consistent with the way the company manages or adjusts those risks, disclosure may include: (a) more details about current positions and perhaps activity during the period, (b) the hypothetical effects on comprehensive income (or net assets), or annual income, of several possible changes in market prices, (c) a gap analysis of interest rate re-pricing or maturity dates, (d) the duration of the financial instruments, (e) the entity's value at risk from derivatives and from other positions at the end of the reporting period and the average value at risk during the year, or (f) other ways of reporting quantitative information as internally developed.

+ References + Details

Derivatives (Tables)

9 Months Ended

Sep. 30, 2017

Derivative Instruments And Hedging Activities Disclosure [Abstract]

Summary of Interest-Rate Swaps Designated as Cash Flow Hedges

Summary information about the interest-rate swaps designated as cash flow hedges was as follows (dollars in thousands):

	September 30, 2017			December 31, 2016
Notional amounts	$	20,000		$	20,000
Weighted average pay rates		3.54	%		3.54	%
Weighted average receive rates	3 month LIBOR			3 month LIBOR
Weighted average maturity	5.7 years			6.5 years
Fair value	$	(1,658	)	$	(1,535	)
Amount of unrealized loss recognized in accumulated other comprehensive income, net of tax	$	(1,023	)	$	(947	)

Summary of Customer Related Interest Rate Swaps

A summary of the Company’s customer related interest rate swaps was as follows (dollars in thousands):

	September 30, 2017					December 31, 2016
	Notional		Estimated			Notional		Estimated
	amount		fair value			amount		fair value
Interest rate swap agreements:
Pay fixed/receive variable swaps	$	46,021	$	(250	)	$	41,254	$	(460	)
Pay variable/receive fixed swaps		46,021		250			41,254		460
Total	$	92,042	$	—		$	82,508	$	—

Stock Options and Restricted Shares (Tables)

9 Months Ended

Sep. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Company Recognized Stock-Based Compensation Expense

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2017			2016			2017			2016
Stock-based compensation expense before income taxes	$	288		$	212		$	771		$	643
Less: deferred tax benefit		(110	)		(81	)		(295	)		(246	)
Reduction of net income	$	178		$	131		$	476		$	397

Summary of Changes in Company's Nonvested Restricted Shares

A summary of the changes in the Company’s nonvested restricted shares for the nine months ended September 30, 2017 follows:

				Weighted
				Average
	Restricted			Grant Date
Nonvested Shares	Shares			Fair Value
Nonvested at beginning of period		199,641		$	12.34
Granted		37,233			18.05
Vested		(58,921	)		12.24
Forfeited		(3,600	)		13.57
Nonvested at end of period		174,353		$	13.56

Summary of Fair Value of Options Granted Using Weighted Average Assumptions

The fair value of options granted was determined using the following weighted average assumptions as of the grant date:

	2017		2016
Dividend yield		—		—
Expected term (in years)		—		7.48
Expected stock price volatility		—		17.20	%
Risk-free interest rate		—		1.66	%
Pre-vest forfeiture rate		—		10.25	%

Summary of Activity in Stock Options

A summary of the activity in stock options for the nine months ended September 30, 2017 follows:

						Weighted
				Weighted		Average
				Average		Remaining
				Exercise		Contractual
	Shares			Price		Term (years)
Outstanding at beginning of period		1,006,000		$	10.48
Granted		—			—
Exercised		(82,150	)		10.00
Forfeited or expired		—			—
Outstanding at end of period		923,850		$	10.52		2.5
Fully vested and expected to vest		918,437		$	10.51		2.5
Exercisable at end of period		875,100		$	10.43		2.2

Information Related to Stock Options

Information related to stock options during each year follows:

	2017		2016
Intrinsic value of options exercised	$	684,275	$	—
Cash received from option exercises		821,500		—
Tax benefit realized from option exercises		263,446		—
Weighted average fair value of options granted		—		3.16

Regulatory Capital Requirements (Tables)

9 Months Ended

Sep. 30, 2017

Banking And Thrift [Abstract]

Schedule of Capital Amounts and Ratios

The Company’s and the Bank’s capital amounts and ratios as of September 30, 2017 and December 31, 2016 are presented in the following table (dollars in thousands).

	Actual					Minimum capital requirement (1)					Minimum to be well-capitalized (2)
	Amount		Ratio			Amount		Ratio			Amount		Ratio
At September 30, 2017:
Total capital to risk-weighted assets:
CapStar Financial Holdings, Inc.	$	155,426		12.42	%	$	100,130		8.00	%	N/A		N/A
CapStar Bank		141,843		11.33			100,118		8.00		$	125,147		10.00
Tier I capital to risk-weighted assets:
CapStar Financial Holdings, Inc.		141,125		11.28			75,098		6.00		N/A		N/A
CapStar Bank		127,542		10.19			75,088		6.00			100,118		8.00
Common equity Tier 1 capital to risk weighted assets:
CapStar Financial Holdings, Inc.		132,417		10.58			56,323		4.50		N/A		N/A
CapStar Bank		111,334		8.90			56,316		4.50			81,346		6.50
Tier I capital to average assets:
CapStar Financial Holdings, Inc.		141,125		10.36			54,464		4.00		N/A		N/A
CapStar Bank		127,542		9.37			54,463		4.00			68,079		5.00

At December 31, 2016:
Total capital to risk-weighted assets:
CapStar Financial Holdings, Inc.	$	149,616		12.60	%	$	95,028		8.00	%	N/A		N/A
CapStar Bank		126,718		10.67			95,028		8.00		$	118,785		10.00
Tier I capital to risk-weighted assets:
CapStar Financial Holdings, Inc.		137,909		11.61			71,271		6.00		N/A		N/A
CapStar Bank		115,011		9.68			71,271		6.00			95,028		8.00
Common equity Tier 1 capital to risk weighted assets:
CapStar Financial Holdings, Inc.		129,528		10.90			53,453		4.50		N/A		N/A
CapStar Bank		99,130		8.35			53,453		4.50			77,210		6.50
Tier I capital to average assets:
CapStar Financial Holdings, Inc.		137,909		10.46			52,727		4.00		N/A		N/A
CapStar Bank		115,011		8.72			52,727		4.00			65,909		5.00

(1)

(2)

Earnings Per Share (Tables)

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Summary of Basic and Diluted Earnings Per Share

The following is a summary of the basic and diluted earnings per share calculation for the three and nine months ended September 30, 2017 and 2016 (dollars in thousands, except share data):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2017		2016		2017		2016
Basic net income per share calculation:
Numerator – Net income	$	4,419	$	2,109	$	1,409	$	6,169
Denominator – Average common shares outstanding		11,279,364		8,792,665		11,239,093		8,701,596
Basic net income per share	$	0.39	$	0.24	$	0.13	$	0.71
Diluted net income per share calculation:
Numerator – Net income	$	4,419	$	2,109	$	1,409	$	6,169
Denominator – Average common shares outstanding		11,279,364		8,792,665		11,239,093		8,701,596
Dilutive shares contingently issuable		1,471,059		2,006,871		1,518,998		1,981,380
Average diluted common shares outstanding		12,750,423		10,799,536		12,758,091		10,682,976
Diluted net income per share	$	0.35	$	0.20	$	0.11	$	0.58

Fair Value (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis

Assets and liabilities measured at fair value on a recurring basis are summarized below (dollars in thousands):

	Fair value measurements at September 30, 2017
				Quoted prices
				in active		Significant
				markets for		other			Significant
				identical		observable			unobservable
	Carrying			assets		inputs			inputs
	Value			(Level 1)		(Level 2)			(Level 3)
Assets:
Securities available for sale:
U.S. government-sponsored agencies	$	11,299		$	—	$	11,299		$	—
Obligations of states and political subdivisions		19,067			—		19,067			—
Mortgage-backed securities-residential		95,823			—		95,823			—
Asset-backed securities		20,411			—		20,411			—
Total securities available for sale	$	146,600		$	—	$	146,600		$	—
Derivatives:
Interest rate swaps - customer related	$	352		$	—	$	352		$	—
Liabilities:
Derivatives:
Interest rate swaps - customer related	$	(352	)	$	—	$	(352	)	$	—
Interest rate swaps - cash flow hedges		(1,658	)		—		(1,658	)		—
Total derivatives	$	(2,010	)	$	—	$	(2,010	)	$	—

	Fair value measurements at December 31, 2016
				Quoted prices
				in active		Significant
				markets for		other			Significant
				identical		observable			unobservable
	Carrying			assets		inputs			inputs
	Value			(Level 1)		(Level 2)			(Level 3)
Assets:
Securities available for sale:
U.S. government-sponsored agencies	$	9,374		$	—	$	9,374		$	—
Obligations of states and political subdivisions		27,913			—		27,913			—
Mortgage-backed securities-residential		124,595			—		124,595			—
Asset-backed securities		20,473			—		20,473			—
Total securities available for sale	$	182,355		$	—	$	182,355		$	—
Derivatives:
Interest rate swaps - customer related	$	460		$	—	$	460		$	—
Liabilities:
Derivatives:
Interest rate swaps - customer related	$	(460	)	$	—	$	(460	)	$	—
Interest rate swaps - cash flow hedges		(1,535	)		—		(1,535	)		—
Total derivatives	$	(1,995	)	$	—	$	(1,995	)	$	—

Summary of Assets Measured at Fair Value on a Nonrecurring Basis

Assets measured at fair value on a nonrecurring basis are summarized below (dollars in thousands):

Fair value measurements at September 30, 2017

Quoted prices

in active

Significant

markets for

other

Significant

identical

observable

unobservable

Carrying

assets

inputs

Value

(level 1)

(level 2)

(level 3)

Assets:

Impaired loans:

Commercial and industrial

1,432

—

1,432

Fair value measurements at December 31, 2016

Quoted prices

in active

Significant

markets for

other

Significant

identical

observable

unobservable

Carrying

assets

inputs

Value

(level 1)

(level 2)

(level 3)

Assets:

Impaired loans:

Commercial and industrial

1,809

—

1,809

Summary of Quantitative Information About Level 3 Fair Value Measurements for Assets Measured at Fair Value on a Non-recurring Basis

Range

Fair

Valuation

(Weighted-

September 30, 2017

Value

Technique(s)

Unobservable Input(s)

Average)

Impaired loans:

Commercial and industrial

1,432

Sales comparison approach

Appraisal discounts

Range

Fair

Valuation

(Weighted-

December 31, 2016

Value

Technique(s)

Unobservable Input(s)

Average)

Impaired loans:

Commercial and industrial

1,809

Sales comparison approach

Appraisal discounts

Summary of Carrying Value and Fair Values of the Bank's Financial Instruments

The carrying value and estimated fair values of the Bank’s financial instruments at September 30, 2017 and December 31, 2016 were as follows (dollars in thousands):

	September 30, 2017				December 31, 2016
	Carrying				Carrying				Fair value
	amount		Fair value		amount		Fair value		level of input
Financial assets:
Cash and due from banks, interest-bearing deposits in financial institutions	$	69,789	$	69,789	$	63,456	$	63,456	Level 1
Federal funds sold		—		—		16,654		16,654	Level 1
Securities available for sale		146,600		146,600		182,355		182,355	Level 2
Securities held to maturity		45,635		48,980		46,864		49,731	Level 2
Loans held for sale		53,225		54,407		42,111		42,302	Level 2
Restricted equity securities		8,799	N/A			6,032	N/A		N/A
Loans, net of unearned income		974,530		974,551		935,251		934,628	Level 3
Accrued interest receivable		3,849		3,849		3,942		3,942	Level 2
Bank owned life insurance		22,335		22,335		21,900		21,900	Level 2
Other assets		352		352		460		460	Level 2
Financial liabilities:
Deposits		1,091,495		1,050,801		1,128,723		1,088,758	Level 3
Federal Home Loan Bank advances		95,000		94,980		55,000		54,989	Level 2
Accrued interest payable		305		305		212		212	Level 2
Other liabilities		3,800		3,800		5,349		5,349	Level 3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)		9 Months Ended
	Sep. 27, 2016	Sep. 30, 2017	Sep. 30, 2016
Summary Of Significant Accounting Policies [Line Items]
Date of acquisition		Feb. 05, 2016
Common Stock
Summary Of Significant Accounting Policies [Line Items]
Issuance of common stock			1,688,049
Exercise of common stock warrants, shares		48,986	87,666
Initial Public Offering \| Common Stock
Summary Of Significant Accounting Policies [Line Items]
Issuance of common stock	2,972,750
Net proceeds from issuance	$ 21,900,000
Initial Public Offering by the Company \| Common Stock
Summary Of Significant Accounting Policies [Line Items]
Issuance of common stock	1,688,049
Initial Public Offering by certain selling shareholders \| Common Stock
Summary Of Significant Accounting Policies [Line Items]
Issuance of common stock	1,284,701
Preferred shares converted to common stock	731,707
Cashless exercise	79,166
Exercise of common stock warrants, shares	250,000
Net proceeds from issuance	$ 0

Securities - Summary of Amortized Cost and Fair Value of Securities Available for Sale and Held to Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Securities available for sale [Abstract]
Amortized Cost	$ 148,108	$ 186,254
Gross unrealized gains	204	82
Gross unrealized (losses)	(1,712)	(3,981)
Estimated fair value	146,600	182,355
Securities held to maturity [Abstract]
Amortized Cost	45,635	46,864
Gross unrealized gains	3,345	2,874
Gross unrealized (losses)		(7)
Estimated fair value	48,980	49,731
U. S. government agency securities
Securities available for sale [Abstract]
Amortized Cost	11,434	9,517
Gross unrealized gains	18
Gross unrealized (losses)	(153)	(143)
Estimated fair value	11,299	9,374
State and municipal securities
Securities available for sale [Abstract]
Amortized Cost	19,031	28,480
Gross unrealized gains	172	65
Gross unrealized (losses)	(136)	(632)
Estimated fair value	19,067	27,913
Securities held to maturity [Abstract]
Amortized Cost	36,469	36,842
Gross unrealized gains	3,138	2,784
Estimated fair value	39,607	39,626
Mortgage-backed securities
Securities available for sale [Abstract]
Amortized Cost	96,975	126,637
Gross unrealized gains	14	17
Gross unrealized (losses)	(1,166)	(2,059)
Estimated fair value	95,823	124,595
Securities held to maturity [Abstract]
Amortized Cost	3,837	4,687
Gross unrealized gains	77	79
Estimated fair value	3,914	4,766
Asset-backed securities
Securities available for sale [Abstract]
Amortized Cost	20,668	21,620
Gross unrealized (losses)	(257)	(1,147)
Estimated fair value	20,411	20,473
Other debt securities
Securities held to maturity [Abstract]
Amortized Cost	5,329	5,335
Gross unrealized gains	130	11
Gross unrealized (losses)		(7)
Estimated fair value	$ 5,459	$ 5,339

Securities - Summary of Securities with Unrealized Losses and Length of Time Continuous Loss Positions (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Available-for-sale securities, continuous unrealized loss position [Abstract]
Less than 12 months, Estimated fair value	$ 76,268	$ 142,245
Less than 12 months, Gross unrealized (losses)	(763)	(2,737)
12 months or more, Estimated fair value	56,873	24,623
12 months or more, Gross unrealized losses	(949)	(1,251)
Total, Estimated fair value	133,141	166,868
Total, Gross unrealized losses	(1,712)	(3,988)
U. S. government agency securities
Available-for-sale securities, continuous unrealized loss position [Abstract]
Less than 12 months, Estimated fair value	9,303	9,374
Less than 12 months, Gross unrealized (losses)	(153)	(143)
Total, Estimated fair value	9,303	9,374
Total, Gross unrealized losses	(153)	(143)
State and municipal securities
Available-for-sale securities, continuous unrealized loss position [Abstract]
Less than 12 months, Estimated fair value	4,968	20,279
Less than 12 months, Gross unrealized (losses)	(19)	(632)
12 months or more, Estimated fair value	6,103
12 months or more, Gross unrealized losses	(117)
Total, Estimated fair value	11,071	20,279
Total, Gross unrealized losses	(136)	(632)
Mortgage-backed securities
Available-for-sale securities, continuous unrealized loss position [Abstract]
Less than 12 months, Estimated fair value	61,997	110,563
Less than 12 months, Gross unrealized (losses)	(591)	(1,955)
12 months or more, Estimated fair value	30,360	4,150
12 months or more, Gross unrealized losses	(575)	(104)
Total, Estimated fair value	92,357	114,713
Total, Gross unrealized losses	(1,166)	(2,059)
Asset-backed securities
Available-for-sale securities, continuous unrealized loss position [Abstract]
12 months or more, Estimated fair value	20,410	20,473
12 months or more, Gross unrealized losses	(257)	(1,147)
Total, Estimated fair value	20,410	20,473
Total, Gross unrealized losses	$ (257)	(1,147)
Other debt securities
Available-for-sale securities, continuous unrealized loss position [Abstract]
Less than 12 months, Estimated fair value		2,029
Less than 12 months, Gross unrealized (losses)		(7)
Total, Estimated fair value		2,029
Total, Gross unrealized losses		$ (7)

Securities - Additional Information (Details) $ in Millions	9 Months Ended
Securities - Additional Information (Details) $ in Millions	Sep. 30, 2017 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Unrealized losses in investment securities portfolio	$ 1.7
Public Deposits, Derivative Positions and Federal Home Loan Bank Advances
Schedule Of Available For Sale Securities [Line Items]
Carrying value of securities	$ 127.1

Securities - Summary of Proceeds from Sales of Securities and Associated Gains and Losses (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Investments Debt And Equity Securities [Abstract]
Proceeds	$ 34,299	$ 46,700
Gross gains	99	244
Gross losses	$ (57)	$ (123)

Securities - Summary of Amortized Cost and Fair Value of Debt and Equity Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Available-for-sale, Amortized cost [Abstract]
Due one to five years	$ 11,388
Due five to ten years	17,970
Due beyond ten years	1,107
Amortized Cost	148,108	$ 186,254
Available-for-sale, Estimated fair value [Abstract]
Due one to five years	11,511
Due five to ten years	17,788
Due beyond ten years	1,067
Estimated fair value	146,600	182,355
Held-to-maturity, Amortized cost [Abstract]
Due one to five years	27,299
Due five to ten years	14,069
Due beyond ten years	430
Mortgage-backed securities	3,837
Amortized Cost	45,635	46,864
Securities held to maturity [Abstract]
Due one to five years	29,448
Due five to ten years	15,129
Due beyond ten years	489
Mortgage-backed securities	3,914
Estimated fair value	48,980	49,731
Mortgage-backed securities
Available-for-sale, Amortized cost [Abstract]
Amortized cost	96,975
Amortized Cost	96,975	126,637
Available-for-sale, Estimated fair value [Abstract]
Estimated fair value	95,823
Estimated fair value	95,823	124,595
Held-to-maturity, Amortized cost [Abstract]
Amortized Cost	3,837	4,687
Securities held to maturity [Abstract]
Estimated fair value	3,914	4,766
Asset-backed securities
Available-for-sale, Amortized cost [Abstract]
Amortized cost	20,668
Amortized Cost	20,668	21,620
Available-for-sale, Estimated fair value [Abstract]
Estimated fair value	20,411
Estimated fair value	$ 20,411	$ 20,473

Loans and Allowance for Loan Losses - Summary of Loan Portfolio (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Loans And Leases Receivable Disclosure [Line Items]
Total loans	$ 974,889		$ 936,218
Less net unearned income	(359)		(967)
Loans, net of unearned income	974,530		935,251
Allowance for loan losses	(14,122)	$ (12,454)	(11,634)	$ (11,510)	$ (10,454)	$ (10,132)
Loans, net	960,408		923,617
Commercial real estate
Loans And Leases Receivable Disclosure [Line Items]
Total loans	366,778		302,322
Allowance for loan losses	(3,294)	(3,533)	(2,655)	(2,420)	(2,596)	(2,879)
Consumer real estate
Loans And Leases Receivable Disclosure [Line Items]
Total loans	100,811		97,015
Allowance for loan losses	(984)	(1,081)	(1,013)	(972)	(968)	(968)
Construction and land development
Loans And Leases Receivable Disclosure [Line Items]
Total loans	79,951		94,491
Allowance for loan losses	(1,487)	(911)	(1,574)	(1,664)	(943)	(914)
Commercial and industrial
Loans And Leases Receivable Disclosure [Line Items]
Total loans	394,600		379,620
Allowance for loan losses	(7,949)	(6,395)	(5,618)	(5,568)	(5,037)	(4,693)
Consumer
Loans And Leases Receivable Disclosure [Line Items]
Total loans	6,289		5,974
Allowance for loan losses	(79)	(57)	(76)	(86)	(104)	(103)
Other
Loans And Leases Receivable Disclosure [Line Items]
Total loans	26,460		56,796
Allowance for loan losses	$ (329)	$ (477)	$ (698)	$ (800)	$ (806)	$ (575)

Loans and Allowance for Loan Losses - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) Contract	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) Contract	Sep. 30, 2016 USD ($) Contract	Dec. 31, 2016 USD ($)
Loans And Leases Receivable Disclosure [Line Items]
Minimum loan amount for loans analyzed by credit risk			$ 500,000
Total loans	$ 974,889,000		974,889,000		$ 936,218,000
Interest income recognized on a cash basis for impaired loans	0	$ 0	0	$ 0
Investment in TDR	1,200,000		1,200,000		1,300,000
Specific allowance related to loans	500,000		500,000		500,000
Additional commitments related to TDR	$ 0		$ 0		0
New TDR identified during the period \| Contract	0		0	1
TDR, payment default within twelve months \| Contract	0		0	1
Loan period considered as payment default			30 days
Consumer
Loans And Leases Receivable Disclosure [Line Items]
Total loans	$ 6,289,000		$ 6,289,000		5,974,000
TDR, payment default within twelve months \| Contract				1
Allowance for loan and lease losses, specific reserve				$ 0
Subsequent default TDR charge-off				$ 100,000
Troubled Debt Restructurings
Loans And Leases Receivable Disclosure [Line Items]
Specific allowance related to loans	0		0		0
Doubtful
Loans And Leases Receivable Disclosure [Line Items]
Total loans	$ 0		$ 0		$ 0

Loans and Allowance for Loan Losses - Summary of Loan Balances by Category as well as Risk Rating (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 974,889	$ 936,218
Total Impaired Loans
Financing Receivable Recorded Investment [Line Items]
Total loans	3,165	3,619
Performing Loans
Financing Receivable Recorded Investment [Line Items]
Total loans	971,724	932,599
Performing Loans \| Pass/Watch
Financing Receivable Recorded Investment [Line Items]
Total loans	949,411	904,836
Performing Loans \| Special Mention
Financing Receivable Recorded Investment [Line Items]
Total loans	16,443	11,035
Performing Loans \| Substandard
Financing Receivable Recorded Investment [Line Items]
Total loans	5,870	16,728
Commercial real estate
Financing Receivable Recorded Investment [Line Items]
Total loans	366,778	302,322
Commercial real estate \| Total Impaired Loans
Financing Receivable Recorded Investment [Line Items]
Total loans	1,233	1,310
Commercial real estate \| Performing Loans
Financing Receivable Recorded Investment [Line Items]
Total loans	365,545	301,012
Commercial real estate \| Performing Loans \| Pass/Watch
Financing Receivable Recorded Investment [Line Items]
Total loans	365,545	301,012
Consumer real estate
Financing Receivable Recorded Investment [Line Items]
Total loans	100,811	97,015
Consumer real estate \| Performing Loans
Financing Receivable Recorded Investment [Line Items]
Total loans	100,811	97,015
Consumer real estate \| Performing Loans \| Pass/Watch
Financing Receivable Recorded Investment [Line Items]
Total loans	100,522	96,722
Consumer real estate \| Performing Loans \| Substandard
Financing Receivable Recorded Investment [Line Items]
Total loans	289	293
Construction and land development
Financing Receivable Recorded Investment [Line Items]
Total loans	79,951	94,491
Construction and land development \| Performing Loans
Financing Receivable Recorded Investment [Line Items]
Total loans	79,951	94,491
Construction and land development \| Performing Loans \| Pass/Watch
Financing Receivable Recorded Investment [Line Items]
Total loans	79,951	94,491
Commercial and industrial
Financing Receivable Recorded Investment [Line Items]
Total loans	394,600	379,620
Commercial and industrial \| Total Impaired Loans
Financing Receivable Recorded Investment [Line Items]
Total loans	1,932	2,309
Commercial and industrial \| Performing Loans
Financing Receivable Recorded Investment [Line Items]
Total loans	392,668	377,311
Commercial and industrial \| Performing Loans \| Pass/Watch
Financing Receivable Recorded Investment [Line Items]
Total loans	370,657	349,857
Commercial and industrial \| Performing Loans \| Special Mention
Financing Receivable Recorded Investment [Line Items]
Total loans	16,443	11,035
Commercial and industrial \| Performing Loans \| Substandard
Financing Receivable Recorded Investment [Line Items]
Total loans	5,568	16,419
Consumer
Financing Receivable Recorded Investment [Line Items]
Total loans	6,289	5,974
Consumer \| Performing Loans
Financing Receivable Recorded Investment [Line Items]
Total loans	6,289	5,974
Consumer \| Performing Loans \| Pass/Watch
Financing Receivable Recorded Investment [Line Items]
Total loans	6,276	5,958
Consumer \| Performing Loans \| Substandard
Financing Receivable Recorded Investment [Line Items]
Total loans	13	16
Other
Financing Receivable Recorded Investment [Line Items]
Total loans	26,460	56,796
Other \| Performing Loans
Financing Receivable Recorded Investment [Line Items]
Total loans	26,460	56,796
Other \| Performing Loans \| Pass/Watch
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 26,460	$ 56,796

Loans and Allowance for Loan Losses - Summary of Changes in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	$ 12,454	$ 10,454	$ 11,634	$ 10,132
Charged-off loans		(645)	(12,369)	(1,452)
Recoveries	1,863	62	1,957	71
Provision for loan losses	(195)	1,639	12,900	2,759
Ending Balance	14,122	11,510	14,122	11,510
Commercial real estate
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	3,533	2,596	2,655	2,879
Charged-off loans				(350)
Recoveries	3	52	4	52
Provision for loan losses	(242)	(228)	635	(161)
Ending Balance	3,294	2,420	3,294	2,420
Consumer real estate
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	1,081	968	1,013	968
Provision for loan losses	(97)	4	(29)	4
Ending Balance	984	972	984	972
Construction and land development
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	911	943	1,574	914
Provision for loan losses	576	721	(87)	750
Ending Balance	1,487	1,664	1,487	1,664
Commercial and industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	6,395	5,037	5,618	4,693
Charged-off loans		(645)	(12,369)	(956)
Recoveries	1,860	10	1,862	18
Provision for loan losses	(306)	1,166	12,838	1,813
Ending Balance	7,949	5,568	7,949	5,568
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	57	104	76	103
Charged-off loans				(146)
Recoveries			91	1
Provision for loan losses	22	(18)	(88)	128
Ending Balance	79	86	79	86
Other
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	477	806	698	575
Provision for loan losses	(148)	(6)	(369)	225
Ending Balance	$ 329	$ 800	$ 329	$ 800

Loans and Allowance for Loan Losses - Summary of Breakdown of Allowance for Loan Losses and Loan Portfolio by Loan Category (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Allowance for Loan Losses:
Collectively evaluated for impairment	$ 13,622		$ 11,134
Individually evaluated for impairment	500		500
Allowance for Loan Losses, Ending Balance	14,122	$ 12,454	11,634	$ 11,510	$ 10,454	$ 10,132
Loans:
Collectively evaluated for impairment	971,724		932,599
Individually evaluated for impairment	3,165		3,619
Total	974,889		936,218
Commercial real estate
Allowance for Loan Losses:
Collectively evaluated for impairment	3,294		2,655
Individually evaluated for impairment	0
Allowance for Loan Losses, Ending Balance	3,294	3,533	2,655	2,420	2,596	2,879
Loans:
Collectively evaluated for impairment	365,545		301,012
Individually evaluated for impairment	1,233		1,310
Total	366,778		302,322
Consumer real estate
Allowance for Loan Losses:
Collectively evaluated for impairment	984		1,013
Individually evaluated for impairment	0
Allowance for Loan Losses, Ending Balance	984	1,081	1,013	972	968	968
Loans:
Collectively evaluated for impairment	100,811		97,015
Individually evaluated for impairment			0
Total	100,811		97,015
Construction and land development
Allowance for Loan Losses:
Collectively evaluated for impairment	1,487		1,574
Individually evaluated for impairment	0
Allowance for Loan Losses, Ending Balance	1,487	911	1,574	1,664	943	914
Loans:
Collectively evaluated for impairment	79,951		94,491
Individually evaluated for impairment			0
Total	79,951		94,491
Commercial and industrial
Allowance for Loan Losses:
Collectively evaluated for impairment	7,449		5,118
Individually evaluated for impairment	500		500
Allowance for Loan Losses, Ending Balance	7,949	6,395	5,618	5,568	5,037	4,693
Loans:
Collectively evaluated for impairment	392,668		377,311
Individually evaluated for impairment	1,932		2,309
Total	394,600		379,620
Consumer
Allowance for Loan Losses:
Collectively evaluated for impairment	79		76
Individually evaluated for impairment	0
Allowance for Loan Losses, Ending Balance	79	57	76	86	104	103
Loans:
Collectively evaluated for impairment	6,289		5,974
Individually evaluated for impairment			0
Total	6,289		5,974
Other
Allowance for Loan Losses:
Collectively evaluated for impairment	329		698
Individually evaluated for impairment	0
Allowance for Loan Losses, Ending Balance	329	$ 477	698	$ 800	$ 806	$ 575
Loans:
Collectively evaluated for impairment	26,460		56,796
Individually evaluated for impairment			0
Total	$ 26,460		$ 56,796

Loans and Allowance for Loan Losses - Allocation of ALL with Corresponding Percentage of ALL in Each Category to Total Loans, Net of Deferred Fee (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan losses, Amount	$ 14,122	$ 12,454	$ 11,634	$ 11,510	$ 10,454	$ 10,132
Allowance for loan losses, Percentage of total loans, net of deferred fees	1.45%		1.24%
Commercial real estate
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan losses, Amount	$ 3,294	3,533	$ 2,655	2,420	2,596	2,879
Allowance for loan losses, Percentage of total loans, net of deferred fees	0.34%		0.28%
Consumer real estate
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan losses, Amount	$ 984	1,081	$ 1,013	972	968	968
Allowance for loan losses, Percentage of total loans, net of deferred fees	0.10%		0.11%
Construction and land development
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan losses, Amount	$ 1,487	911	$ 1,574	1,664	943	914
Allowance for loan losses, Percentage of total loans, net of deferred fees	0.15%		0.17%
Commercial and industrial
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan losses, Amount	$ 7,949	6,395	$ 5,618	5,568	5,037	4,693
Allowance for loan losses, Percentage of total loans, net of deferred fees	0.82%		0.60%
Consumer
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan losses, Amount	$ 79	57	$ 76	86	104	103
Allowance for loan losses, Percentage of total loans, net of deferred fees	0.01%		0.01%
Other
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan losses, Amount	$ 329	$ 477	$ 698	$ 800	$ 806	$ 575
Allowance for loan losses, Percentage of total loans, net of deferred fees	0.03%		0.07%

Loans and Allowance for Loan Losses - Summary of Impaired Loans Evaluated for Specific Loss Allowance (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance recorded, Recorded investment	$ 1,233	$ 1,310
Impaired loans with no related allowance recorded, Unpaid principal balance	1,660	1,686
Impaired loans with an allowance recorded, Related allowance	500	500
Impaired loans with an allowance recorded, Recorded investment	1,932	2,309
Impaired loans with an allowance recorded, Unpaid principal balance	2,770	2,921
Recorded investment	3,165	3,619
Unpaid principal balance	4,430	4,607
Commercial real estate
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance recorded, Recorded investment	1,233	1,310
Impaired loans with no related allowance recorded, Unpaid principal balance	1,660	1,686
Commercial and industrial
Financing Receivable Impaired [Line Items]
Impaired loans with an allowance recorded, Related allowance	500	500
Impaired loans with an allowance recorded, Recorded investment	1,932	2,309
Impaired loans with an allowance recorded, Unpaid principal balance	$ 2,770	$ 2,921

Loans and Allowance for Loan Losses - Summary of Average Recorded Investment and Interest Income Recognized on Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance recorded, Average recorded investment	$ 1,245		$ 1,272
Impaired loans with an allowance recorded, Average recorded investment	1,941	$ 5,096	2,141	$ 5,276
Impaired loans with an allowance recorded, Interest income recognized				30
Average recorded investment	3,186	5,096	3,413	5,276
Interest income recognized				30
Commercial real estate
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance recorded, Average recorded investment	1,245		1,272
Impaired loans with an allowance recorded, Average recorded investment		1,685		1,742
Commercial and industrial
Financing Receivable Impaired [Line Items]
Impaired loans with an allowance recorded, Average recorded investment	$ 1,941	$ 3,411	$ 2,141	3,534
Impaired loans with an allowance recorded, Interest income recognized				$ 30

Loans and Allowance for Loan Losses - Schedule of Aging of Recorded Investment in Past-due Loans, by Class of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	$ 2,184	$ 363
Loans Not Past Due	972,705	935,855
Total	974,889	936,218
Commercial real estate
Financing Receivable Recorded Investment Past Due [Line Items]
Loans Not Past Due	366,778	302,322
Total	366,778	302,322
Consumer real estate
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	785	363
Loans Not Past Due	100,026	96,652
Total	100,811	97,015
Construction and land development
Financing Receivable Recorded Investment Past Due [Line Items]
Loans Not Past Due	79,951	94,491
Total	79,951	94,491
Commercial and industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	1,398
Loans Not Past Due	393,202	379,620
Total	394,600	379,620
Consumer
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	1
Loans Not Past Due	6,288	5,974
Total	6,289	5,974
Other
Financing Receivable Recorded Investment Past Due [Line Items]
Loans Not Past Due	26,460	56,796
Total	26,460	56,796
30 - 59 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	1,660	81
30 - 59 Days Past Due [Member] \| Consumer real estate
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	506	81
30 - 59 Days Past Due [Member] \| Commercial and industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	1,154
60 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	497	282
60 - 89 Days Past Due [Member] \| Consumer real estate
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	279	$ 282
60 - 89 Days Past Due [Member] \| Commercial and industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	218
60 - 89 Days Past Due [Member] \| Consumer
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	1
Greater than 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	27
Greater than 89 Days Past Due [Member] \| Commercial and industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	$ 27

Loans and Allowance for Loan Losses - Schedule of Non-Accrual Loans, Past Due Loans over 90 Days Outstanding and Accruing and Troubled Debt Restructurings (TDR) by Class of Loans (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2017
Accounts Notes And Loans Receivable [Line Items]
Non-Accrual		$ 3,619	$ 3,165
Past Due Over 90 Days and Accruing			27
Troubled Debt Restructurings	$ 1,222	1,272
Commercial real estate
Accounts Notes And Loans Receivable [Line Items]
Non-Accrual		1,310	1,233
Troubled Debt Restructurings	$ 1,222	1,272
Commercial and industrial
Accounts Notes And Loans Receivable [Line Items]
Non-Accrual		$ 2,309	1,932
Past Due Over 90 Days and Accruing			$ 27

Loans and Allowance for Loan Losses - Schedule of Loans by Class Modified as TDR (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017 Contract	Sep. 30, 2017 Contract	Sep. 30, 2016 USD ($) Contract
Financing Receivable Modifications [Line Items]
Number of contracts \| Contract	0	0	1
Pre modification outstanding recorded investment			$ 1,948
Post modification outstanding recorded investment, net of related allowance			$ 1,170
Commercial real estate
Financing Receivable Modifications [Line Items]
Number of contracts \| Contract			1
Pre modification outstanding recorded investment			$ 1,948
Post modification outstanding recorded investment, net of related allowance			$ 1,170

Loans and Allowance for Loan Losses - Schedule of Loans by Class Modified as TDR for Which There Was Payment Default Within Twelve Months Following Modification (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017 Contract	Sep. 30, 2017 Contract	Sep. 30, 2016 USD ($) Contract
Financing Receivable Modifications [Line Items]
Number of contracts \| Contract	0	0	1
Recorded investment \| $			$ 124
Consumer
Financing Receivable Modifications [Line Items]
Number of contracts \| Contract			1
Recorded investment \| $			$ 124

Federal Home Loan Bank Advances - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Federal Home Loan Bank Advances [Line Items]
Outstanding borrowings	$ 95,000	$ 55,000
Investment securities, FHLB stock and commercial and residential real estate mortgage loans
Federal Home Loan Bank Advances [Line Items]
Mortgage loans collateralized amount	367,000
Amount of available credit	$ 108,000

Federal Home Loan Bank Advances - Summary of Contractual Maturities and Average Effective Rates of Outstanding Advances (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Federal Home Loan Bank Advances Maturities Summary [Abstract]
2017	$ 60,000
2017		$ 55,000
2018	35,000
Total amount	$ 95,000	$ 55,000
2017	1.18%	0.80%
2018	1.50%
Total interest rates	1.30%	0.80%

Accumulated Other Comprehensive Income (Loss) - Summary of Changes In Accumulated Other Comprehensive Income (Loss) By Component, Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance			$ 139,207	$ 108,586
Other comprehensive income (loss) before reclassification, net of tax			1,309	660
Amounts reclassified from accumulated other comprehensive income (loss), net of tax			663	263
Other comprehensive income (loss)	$ 583	$ (289)	1,972	923
Ending balance	144,204	138,427	144,204	138,427
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance			(4,241)	(3,704)
Other comprehensive income (loss) before reclassification, net of tax			(193)	(1,086)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax			589	261
Other comprehensive income (loss)			396	(825)
Ending balance	(3,845)	(4,529)	(3,845)	(4,529)
Unrealized Gains and Losses on Available for Sale Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance			(698)	105
Other comprehensive income (loss) before reclassification, net of tax			1,502	1,746
Amounts reclassified from accumulated other comprehensive income (loss), net of tax			(26)	(75)
Other comprehensive income (loss)			1,476	1,671
Ending balance	778	1,776	778	1,776
Unrealized Losses on Securities Transferred to Held to Maturity
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance			(1,212)	(1,315)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax			100	77
Other comprehensive income (loss)			100	77
Ending balance	(1,112)	(1,238)	(1,112)	(1,238)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance			(6,151)	(4,914)
Other comprehensive income (loss)			1,972	923
Ending balance	$ (4,179)	$ (3,991)	$ (4,179)	$ (3,991)

Accumulated Other Comprehensive Income (Loss) - Summary of Significant Amounts Reclassified out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Net (gain) loss on sale of securities			$ (42)	$ (121)
Interest expense - Federal Home Loan Bank advances	$ 563	$ 97	1,083	280
Income tax expense (benefit)	1,516	1,042	141	2,998
Net of tax	(4,419)	(2,109)	(1,409)	(6,169)
Reclassification out of Accumulated Other Comprehensive Income \| Unrealized Losses on Cash Flow Hedges
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Interest expense money market	109	38	322	113
Interest expense - Federal Home Loan Bank advances	168	50	267	148
Net of tax	277	88	589	261
Reclassification out of Accumulated Other Comprehensive Income \| Unrealized (Gains) and Losses on Available for Sale Securities
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Net (gain) loss on sale of securities	(9)	4	(42)	(121)
Income tax expense (benefit)	3	(2)	16	46
Net of tax	(6)	2	(26)	(75)
Reclassification out of Accumulated Other Comprehensive Income \| Unrealized Losses on Securities Transferred to Held to Maturity
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Interest income - securities	79	42	162	125
Income tax expense (benefit)	(30)	(16)	(62)	(48)
Net of tax	$ 49	$ 26	$ 100	$ 77

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Taxes [Line Items]
Effective tax rate	25.50%	33.10%	9.10%	32.70%
Income tax expense	$ (144,000)		$ (310,000)
Federal statutory income tax rate	34.00%	34.00%	34.00%	34.00%
Tennessee \| State and Local Jurisdiction
Income Taxes [Line Items]
Excise tax rate	6.50%	6.50%	6.50%	6.50%

Commitments and Contingencies - Schedule of Financial Instruments Representing Credit Risk (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Unused commitments to extend credit	$ 575,558	$ 508,990
Standby letters of credit	11,535	10,886
Total	$ 587,093	$ 519,876

Derivatives - Additional Information (Details) - Designated as Hedging Instrument - Interest Rate Swaps - Cash Flow Hedges - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Notional amounts	$ 20,000,000	$ 20,000,000
Investment securities pledged collateral to counterparties	2,700,000
Investment securities pledged collateral from counterparties	$ 0

Derivatives - Summary of Interest-Rate Swaps Designated as Cash Flow Hedges (Details) - Designated as Hedging Instrument - Cash Flow Hedges - Interest Rate Swaps - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Notional amounts	$ 20,000,000	$ 20,000,000
Weighted average pay rates	3.54%	3.54%
Weighted average receive rates	Sep, 2017: 3 month LIBOR and Dec. 31, 2016: 3 month LIBOR
Weighted average maturity	5 years 8 months 12 days	6 years 6 months
Fair value	$ (1,658,000)	$ (1,535,000)
Amount of unrealized loss recognized in accumulated other comprehensive income, net of tax	$ (1,023,000)	$ (947,000)

Derivatives - Summary of Customer Related Interest Rate Swaps (Details) - Interest Rate Swaps - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Interest rate swap, Notional amount	$ 92,042,000	$ 82,508,000
Pay fixed/receive variable swaps
Derivative [Line Items]
Interest rate swap, Notional amount	46,021,000	41,254,000
Interest rate swap, Estimated fair value	(250,000)	(460,000)
Pay variable/receive fixed swaps
Derivative [Line Items]
Interest rate swap, Notional amount	46,021,000	41,254,000
Interest rate swap, Estimated fair value	$ 250,000	$ 460,000

Stock Options and Restricted Shares - Additional Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 1.6
Total fair value of shares vested	$ 1.1	$ 0.5
Vesting period	3 years
Contractual term	10 years
Expected dividend yield	0.00%
Options granted	0
Unrecognized compensation cost	$ 0.1
Restricted Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Cost expected to be recognized over a weighted-average period	1 year 10 months 24 days
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Cost expected to be recognized over a weighted-average period	1 year 9 months 18 days
CapStar Bank 2008 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of stock reserved for issuance of stock incentives	1,569,475
Shares issuable under both restricted share and stock option grants	169,867

Stock Options and Restricted Shares - Summary of Company Recognized Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based compensation expense before income taxes	$ 288	$ 212	$ 771	$ 643
Less: deferred tax benefit	(110)	(81)	(295)	(246)
Reduction of net income	$ 178	$ 131	$ 476	$ 397

Stock Options and Restricted Shares - Summary of Changes in Company's Nonvested Restricted Shares (Details)	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Restricted Shares, Abstract
Restricted Shares, Nonvested Beginning Balance \| shares	199,641
Restricted Shares, Granted \| shares	37,233
Restricted Shares, Vested \| shares	(58,921)
Restricted Shares, Forfeited \| shares	(3,600)
Restricted Shares, Nonvested Ending Balance \| shares	174,353
Weighted Average Grant Date Fair Value, Abstract
Weighted Average Grant Date Fair Value, Nonvested Beginning Balance \| $ / shares	$ 12.34
Weighted Average Grant Date Fair Value, Granted \| $ / shares	18.05
Weighted Average Grant Date Fair Value, Vested \| $ / shares	12.24
Weighted Average Grant Date Fair Value, Forfeited \| $ / shares	13.57
Weighted Average Grant Date Fair Value, Nonvested Ending Balance \| $ / shares	$ 13.56

Stock Options and Restricted Shares - Summary of Fair Value of Options Granted Using Weighted Average Assumptions (Details)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected dividend yield	0.00%
Expected term (in years)	0 years	7 years 5 months 23 days
Expected stock price volatility		17.20%
Risk-free interest rate		1.66%
Pre-vest forfeiture rate		10.25%

Stock Options and Restricted Shares - Summary of Activity in Stock Options (Details)	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Shares, Abstract
Shares Outstanding, Beginning Balance	1,006,000
Shares Outstanding, Granted	0
Shares Outstanding, Exercised	(82,150)
Shares Outstanding, Ending Balance	923,850
Shares, Fully Vested and Expected to Vest	918,437
Shares, Exercisable at End of Period	875,100
Weighted Average Exercise Price, Abstract
Weighted Average Exercise Price Outstanding, Beginning Balance \| $ / shares	$ 10.48
Weighted Average Exercise Price Outstanding, Exercised \| $ / shares	10.00
Weighted Average Exercise Price Outstanding, Ending Balance \| $ / shares	10.52
Weighted Average Exercise Price, Fully vested and expected to vest \| $ / shares	10.51
Weighted Average Exercise Price, Exercisable at End of Period \| $ / shares	$ 10.43
Weighted Average Remaining Contractual Term (year), Abstract
Weighted Average Remaining Contractual Term Outstanding	2 years 6 months
Weighted Average Remaining Contractual Term, Fully Vested and Expected to Vest	2 years 6 months
Weighted Average Remaining Contractual Term, Exercisable at End of Period	2 years 2 months 12 days

Stock Options and Restricted Shares - Information Related to Stock Options (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Intrinsic value of options exercised	$ 684,275
Cash received from option exercises	821,500
Tax benefit realized from option exercises	$ 263,446
Weighted average fair value of options granted		$ 3.16

Regulatory Capital Requirements - Schedule of Capital Amounts and Ratios (Details) - USD ($)
$ in Thousands

Sep. 30, 2017

Dec. 31, 2016

CapStar Financial Holdings, Inc.

Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]

Total capital to risk-weighted assets, actual amount

$ 155,426

$ 149,616

Tier I capital to risk-weighted assets, actual amount

141,125

137,909

Tier I capital to average assets, actual amount

$ 141,125

$ 137,909

Total capital to risk-weighted assets, actual ratio

12.42%

12.60%

Tier I capital to risk-weighted assets, actual ratio

11.28%

11.61%

Tier I capital to average assets, actual ratio

10.36%

10.46%

Total capital to risk-weighted assets, minimum capital requirement amount

^[1]

$ 100,130

$ 95,028

Tier I capital to risk-weighted assets, minimum capital requirement amount

^[1]

75,098

71,271

Tier I capital to average assets, minimum capital requirement amount

^[1]

$ 54,464

$ 52,727

Total capital to risk-weighted assets, minimum capital requirement ratio

^[1]

8.00%

Tier I capital to risk-weighted assets, minimum capital requirement ratio

^[1]

6.00%

Tier I capital to average assets, minimum capital requirement ratio

^[1]

4.00%

CapStar Financial Holdings, Inc. | Common Stock

Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]

Tier I capital to risk-weighted assets, actual amount

$ 132,417

$ 129,528

Tier I capital to risk-weighted assets, actual ratio

10.58%

10.90%

Tier I capital to risk-weighted assets, minimum capital requirement amount

^[1]

$ 56,323

$ 53,453

Tier I capital to risk-weighted assets, minimum capital requirement ratio

^[1]

4.50%

CapStar Bank

Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]

Total capital to risk-weighted assets, actual amount

$ 141,843

$ 126,718

Tier I capital to risk-weighted assets, actual amount

127,542

115,011

Tier I capital to average assets, actual amount

$ 127,542

$ 115,011

Total capital to risk-weighted assets, actual ratio

11.33%

10.67%

Tier I capital to risk-weighted assets, actual ratio

10.19%

9.68%

Tier I capital to average assets, actual ratio

9.37%

8.72%

Total capital to risk-weighted assets, minimum capital requirement amount

^[1]

$ 100,118

$ 95,028

Tier I capital to risk-weighted assets, minimum capital requirement amount

^[1]

75,088

71,271

Tier I capital to average assets, minimum capital requirement amount

^[1]

$ 54,463

$ 52,727

Total capital to risk-weighted assets, minimum capital requirement ratio

^[1]

8.00%

Tier I capital to risk-weighted assets, minimum capital requirement ratio

^[1]

6.00%

Tier I capital to average assets, minimum capital requirement ratio

^[1]

4.00%

Total capital to risk-weighted assets, minimum to be well capitalized amount

^[2]

$ 125,147

$ 118,785

Tier I capital to risk-weighted assets, minimum to be well capitalized amount

^[2]

100,118

95,028

Tier I capital to average assets, minimum to be well capitalized amount

^[2]

$ 68,079

$ 65,909

Total capital to risk-weighted assets, minimum to be well capitalized ratio

^[2]

10.00%

Tier I capital to risk-weighted assets, minimum to be well capitalized ratio

^[2]

8.00%

Tier I capital to average assets, minimum to be well capitalized ratio

^[2]

5.00%

CapStar Bank | Common Stock

Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]

Tier I capital to risk-weighted assets, actual amount

$ 111,334

$ 99,130

Tier I capital to risk-weighted assets, actual ratio

8.90%

8.35%

Tier I capital to risk-weighted assets, minimum capital requirement amount

^[1]

$ 56,316

$ 53,453

Tier I capital to risk-weighted assets, minimum capital requirement ratio

^[1]

4.50%

Tier I capital to risk-weighted assets, minimum to be well capitalized amount

^[2]

$ 81,346

$ 77,210

Tier I capital to risk-weighted assets, minimum to be well capitalized ratio

^[2]

6.50%

[1]	For the calendar year 2017, the Company must maintain a capital conservation buffer of Tier 1 common equity capital in excess of minimum risk-based capital ratios by at least 1.25% to avoid limits on capital distributions and certain discretionary bonus payments to executive officers and similar employees.
[2]	For the Company to be well-capitalized, the Bank must be well-capitalized and the Company must not be subject to any written agreement, order, capital directive, or prompt corrective action directive issued by the Federal Reserve to meet and maintain a specific capital level for any capital measure.

Regulatory Capital Requirements - Schedule of Capital Amounts and Ratios (Parenthetical) (Details)	Sep. 30, 2017
Banking And Thrift [Abstract]
Minimum risk based capital ratios	1.25%

Earning Per Share - Summary of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic net income per share calculation:
Numerator – Net income	$ 4,419	$ 2,109	$ 1,409	$ 6,169
Denominator – Average common shares outstanding	11,279,364	8,792,665	11,239,093	8,701,596
Basic net income per share of common stock	$ 0.39	$ 0.24	$ 0.13	$ 0.71
Diluted net income per share calculation:
Numerator – Net income	$ 4,419	$ 2,109	$ 1,409	$ 6,169
Denominator – Average common shares outstanding	11,279,364	8,792,665	11,239,093	8,701,596
Dilutive shares contingently issuable	1,471,059	2,006,871	1,518,998	1,981,380
Average diluted common shares outstanding	12,750,423	10,799,536	12,758,091	10,682,976
Diluted net income per share of common stock	$ 0.35	$ 0.20	$ 0.11	$ 0.58

Fair Value - Additional Information (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Other real estate owned	$ 0	$ 0
Loans held for sale carried at fair value	$ 0	$ 0

Fair Value - Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets:
Total securities available for sale	$ 146,600	$ 182,355
Obligations of States and Political Subdivisions
Assets:
Total securities available for sale	19,067	27,913
Asset-backed securities
Assets:
Total securities available for sale	20,411	20,473
Fair Value Measurements Recurring Basis
Assets:
Total securities available for sale	146,600	182,355
Liabilities:
Total derivatives	(2,010)	(1,995)
Fair Value Measurements Recurring Basis \| U.S. Government-sponsored Agencies
Assets:
Total securities available for sale	11,299	9,374
Fair Value Measurements Recurring Basis \| Obligations of States and Political Subdivisions
Assets:
Total securities available for sale	19,067	27,913
Fair Value Measurements Recurring Basis \| Mortgage-backed Securities-residential
Assets:
Total securities available for sale	95,823	124,595
Fair Value Measurements Recurring Basis \| Asset-backed securities
Assets:
Total securities available for sale	20,411	20,473
Fair Value Measurements Recurring Basis \| Interest Rate Swaps - Customer Related
Assets:
Interest rate swaps - customer related	352	460
Liabilities:
Total derivatives	(352)	(460)
Fair Value Measurements Recurring Basis \| Interest Rate Swaps - Cash Flow Hedges
Liabilities:
Total derivatives	(1,658)	(1,535)
Fair Value Measurements Recurring Basis \| Significant Other Observable Inputs (Level 2)
Assets:
Total securities available for sale	146,600	182,355
Liabilities:
Total derivatives	(2,010)	(1,995)
Fair Value Measurements Recurring Basis \| Significant Other Observable Inputs (Level 2) \| U.S. Government-sponsored Agencies
Assets:
Total securities available for sale	11,299	9,374
Fair Value Measurements Recurring Basis \| Significant Other Observable Inputs (Level 2) \| Obligations of States and Political Subdivisions
Assets:
Total securities available for sale	19,067	27,913
Fair Value Measurements Recurring Basis \| Significant Other Observable Inputs (Level 2) \| Mortgage-backed Securities-residential
Assets:
Total securities available for sale	95,823	124,595
Fair Value Measurements Recurring Basis \| Significant Other Observable Inputs (Level 2) \| Asset-backed securities
Assets:
Total securities available for sale	20,411	20,473
Fair Value Measurements Recurring Basis \| Significant Other Observable Inputs (Level 2) \| Interest Rate Swaps - Customer Related
Assets:
Interest rate swaps - customer related	352	460
Liabilities:
Total derivatives	(352)	(460)
Fair Value Measurements Recurring Basis \| Significant Other Observable Inputs (Level 2) \| Interest Rate Swaps - Cash Flow Hedges
Liabilities:
Total derivatives	$ (1,658)	$ (1,535)

Fair Value - Summary of Assets Measured at Fair Value on a Nonrecurring Basis (Details) - Fair Value, Measurements, Nonrecurring [Member] - Commercial and industrial - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets:
Impaired loans	$ 1,432	$ 1,809
Significant Unobservable Inputs (Level 3)
Assets:
Impaired loans	$ 1,432	$ 1,809

Fair Value - Summary of Quantitative Information About Level 3 Fair Value Measurements for Assets Measured at Fair Value on a Non-Recurring Basis (Details) - Fair Value, Measurements, Nonrecurring [Member] - Commercial and industrial - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	$ 1,432	$ 1,809
Level 3 Fair Value Measurements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	$ 1,432	$ 1,809
Valuation Technique(s)	Sep. 30, 2017: Sales comparison approach and Dec. 31, 2016: Sales comparison approach
Unobservable Input(s)	Sep. 30, 2017: Appraisal discounts and Dec. 31, 2016: Appraisal discounts
Range (Weighted-Average)	25.00%	25.00%

Fair Value - Summary of Carrying Value and Fair Values of the Bank's Financial Instruments (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Financial assets:
Securities available for sale	$ 146,600,000	$ 182,355,000
Securities held to maturity, fair value	48,980,000	49,731,000
Loans held for sale	0	0
Carrying amount
Financial assets:
Restricted equity securities	8,799,000	6,032,000
Carrying amount \| Level 1
Financial assets:
Cash and due from banks, interest-bearing deposits in financial institutions	69,789,000	63,456,000
Federal funds sold		16,654,000
Carrying amount \| Level 2
Financial assets:
Securities available for sale	146,600,000	182,355,000
Securities held to maturity, fair value	45,635,000	46,864,000
Loans held for sale	53,225,000	42,111,000
Accrued interest receivable	3,849,000	3,942,000
Bank owned life insurance	22,335,000	21,900,000
Other assets	352,000	460,000
Financial liabilities:
Federal Home Loan Bank advances	95,000,000	55,000,000
Accrued interest payable	305,000	212,000
Carrying amount \| Level 3 Fair Value Measurements
Financial assets:
Loans, net of unearned income	974,530,000	935,251,000
Financial liabilities:
Deposits	1,091,495,000	1,128,723,000
Other liabilities	3,800,000	5,349,000
Fair value \| Level 1
Financial assets:
Cash and due from banks, interest-bearing deposits in financial institutions	69,789,000	63,456,000
Federal funds sold		16,654,000
Fair value \| Level 2
Financial assets:
Securities available for sale	146,600,000	182,355,000
Securities held to maturity, fair value	48,980,000	49,731,000
Loans held for sale	54,407,000	42,302,000
Accrued interest receivable	3,849,000	3,942,000
Bank owned life insurance	22,335,000	21,900,000
Other assets	352,000	460,000
Financial liabilities:
Federal Home Loan Bank advances	94,980,000	54,989,000
Accrued interest payable	305,000	212,000
Fair value \| Level 3 Fair Value Measurements
Financial assets:
Loans, net of unearned income	974,551,000	934,628,000
Financial liabilities:
Deposits	1,050,801,000	1,088,758,000
Other liabilities	$ 3,800,000	$ 5,349,000