v3.26.1
Borrowings - Additional Information (Detail) - USD ($)
3 Months Ended
Jul. 17, 2025
Sep. 26, 2023
Sep. 15, 2023
Jul. 12, 2023
Feb. 10, 2023
Jun. 29, 2020
Mar. 31, 2026
Dec. 31, 2025
Jul. 23, 2020
Debt Instrument [Line Items]                  
Line of credit facility maximum borrowing capacity         $ 25,000,000        
Debt Instrument, Maturity Date         Feb. 10, 2024        
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage         20.00%        
Debt instrument floating daily, floor Interest Rate         3.25%        
Trust Preferred Securities [Member] | FCB Capital Trust II [Member]                  
Debt Instrument [Line Items]                  
Debt Instrument, Maturity Date             Apr. 15, 2035    
Subordinated debenture basis spread on variable rate             2.00%    
Preferred securities liquidation spread percent       2.00%          
Trust Preferred Securities [Member] | FCB Capital Trust II [Member] | Tenor Spread Adjustment [Member]                  
Debt Instrument [Line Items]                  
Preferred securities liquidation spread percent       0.26%          
Trust Preferred Securities [Member] | FCB Capital Trust III [Member]                  
Debt Instrument [Line Items]                  
Debt Instrument, Maturity Date             Jun. 15, 2037    
Subordinated debenture basis spread on variable rate             1.89%    
Preferred securities liquidation spread percent     1.89%            
Trust Preferred Securities [Member] | FCB Capital Trust III [Member] | Tenor Spread Adjustment [Member]                  
Debt Instrument [Line Items]                  
Preferred securities liquidation spread percent     0.26%            
Trust Preferred Securities [Member] | Community First Statutory Trust I [Member]                  
Debt Instrument [Line Items]                  
Debt Instrument, Maturity Date             Dec. 26, 2032    
Subordinated debenture basis spread on variable rate             3.25%    
Preferred securities liquidation spread percent   3.25%              
Trust Preferred Securities [Member] | Community First Statutory Trust I [Member] | Tenor Spread Adjustment [Member]                  
Debt Instrument [Line Items]                  
Preferred securities liquidation spread percent   0.26%              
Trust Preferred Securities [Member] | American State Bank Statutory Trust I [Member]                  
Debt Instrument [Line Items]                  
Debt Instrument, Maturity Date             Sep. 15, 2035    
Subordinated debenture basis spread on variable rate             1.80%    
Preferred securities liquidation spread percent     1.80%            
Trust Preferred Securities [Member] | American State Bank Statutory Trust I [Member] | Tenor Spread Adjustment [Member]                  
Debt Instrument [Line Items]                  
Preferred securities liquidation spread percent     0.26%            
Federal Home Loan Bank Advances [Member]                  
Debt Instrument [Line Items]                  
Letter of credit             $ 59,742,000 $ 64,635,000  
Line of credit facility additional borrowing capacity             494,792,000 567,399,000  
Federal Home Loan Bank Advances [Member] | Qualifying Loans [Member]                  
Debt Instrument [Line Items]                  
Line of credit facility maximum borrowing capacity             904,073,000 932,939,000  
Federal Reserve Bank Borrowings [Member]                  
Debt Instrument [Line Items]                  
Line of credit facility maximum borrowing capacity             2,142,985,000 1,863,782,000  
Federal Reserve Bank Borrowings [Member] | Asset Pledged as Collateral without Right [Member]                  
Debt Instrument [Line Items]                  
Pledged loan outstanding balance             2,622,634,000 2,456,465,000  
Federal Reserve's Bank Term Funding Program [Member]                  
Debt Instrument [Line Items]                  
Secured borrowings from this facility             0 0  
Bank Stock Loan [Member]                  
Debt Instrument [Line Items]                  
Bank stock loan             $ 0 0  
Residential Mortgage-Backed Securities (Issued by Government-Sponsored Entities) [Member]                  
Debt Instrument [Line Items]                  
Debt Instrument, Maturity Date           Jun. 30, 2030      
Subordinated notes aggregate principal amount           $ 42,000,000     $ 33,000,000
Subordinated notes commencement date           Dec. 30, 2020      
Debt instrument interest rate percentage           7.00%      
Subordinated notes description             From June 29, 2020, through June 29, 2025, the Company will pay interest on the notes semi-annually in arrears on June 30 and December 30 of each year, commencing on December 30, 2020, at a fixed interest rate of 7.00%. Beginning June 30, 2025, the notes convert to a floating interest rate, to be reset quarterly, equal to the then-current Three-Month Term SOFR, as defined in the Indenture, plus 688 basis points. Interest payments during the floating-rate period will be paid quarterly in arrears on March 30, June 30, September 30 and December 30 of each year, commencing on September 30, 2025.    
Debt instrument, frequency of periodic payment             semi-annually    
7.125% Fixed-to-Floating Rate Subordinated Notes Due 2035 [Member]                  
Debt Instrument [Line Items]                  
Debt Instrument, Maturity Date Aug. 01, 2035                
Subordinated notes aggregate principal amount $ 75,000,000           $ 75,000,000 75,000,000  
Subordinated notes commencement date Feb. 01, 2026                
Debt instrument interest rate percentage 7.125%                
Subordinated notes description             From July 17, 2025, through August 1, 2030, the Company will pay interest on the notes semi-annually in arrears on February 1 and August 1 of each year, commencing on February 1, 2026, at a fixed interest rate of 7.125%. Beginning August 1, 2030, the notes convert to a floating interest rate, to be reset quarterly, equal to the then-current Three-Month Term SOFR, as defined in the Indenture, plus 349 basis points for each quarterly interest period during the floating rate period. Interest payments during the floating-rate period will be paid quarterly in arrears on February 1, May 1, August 1 and November 1 of each year, commencing on November 1, 2030.    
Debt instrument, frequency of periodic payment             semi-annually    
Subordinated notes variable interest rate percentage SOFR, as defined in the Indenture, plus 349 basis points                
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration] SOFR plus [Member]                
Government-Sponsored Residential Mortgage-Backed Securities [Member]                  
Debt Instrument [Line Items]                  
Residential mortgage-backed securities, fair value             $ 39,826,000 $ 41,481,000