v3.10.0.1
Document and Entity Information - shares
6 Months Ended
Jun. 30, 2018
Jul. 30, 2018
Document And Entity Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q2  
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 Accelerated Filer  
Voting    
Document And Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   11,850,622
Nonvoting    
Document And Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   132,561