v3.26.1
Investment Securities - Maturity of Securities Available for Sale (Detail) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Net Investment Income [Line Items]    
Due within one year, Estimated Fair Value $ 991  
Due after one but within five years, Amortized Cost 30,298  
Due after one but within five years, Estimated Fair Value 29,805  
Due after five but within ten years, Amortized Cost 19,512  
Due after five but within ten years, Estimated Fair Value 18,686  
Due after ten years, Amortized Cost 0  
Due after ten years, Estimated Fair Value 0  
Due within one year, Amortized Cost 50,810  
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost 1,000  
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value 49,482  
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost 1,079,100  
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value 992,917  
Amortized Cost 1,129,910 $ 1,096,232
Securities available for sale, at fair value 1,042,399 $ 1,014,194
Debt Securities [Member]    
Net Investment Income [Line Items]    
Amortized Cost 1,129,910  
Securities available for sale, at fair value 1,042,399  
US Government Agencies Debt Securities [Member]    
Net Investment Income [Line Items]    
Amortized Cost 711,900  
Securities available for sale, at fair value 667,800  
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Net Investment Income [Line Items]    
Amortized Cost 367,200  
Securities available for sale, at fair value $ 325,200