v3.26.1
Investment Securities - Maturity of Securities Available for Sale (Detail) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Net Investment Income [Line Items]    
Due within one year, Estimated Fair Value $ 998  
Due after one but within five years, Amortized Cost 27,636  
Due after one but within five years, Estimated Fair Value 26,903  
Due after five but within ten years, Amortized Cost 22,028  
Due after five but within ten years, Estimated Fair Value 21,471  
Due after ten years, Amortized Cost 0  
Due after ten years, Estimated Fair Value 0  
Due within one year, Amortized Cost 50,664  
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 49,372  
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost 1,132,586  
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value 1,042,829  
Amortized Cost 1,183,250 $ 1,096,232
Securities available for sale, at fair value 1,092,201 $ 1,014,194
Debt Securities [Member]    
Net Investment Income [Line Items]    
Amortized Cost 1,183,250  
Securities available for sale, at fair value 1,092,201  
US Government Agencies Debt Securities [Member]    
Net Investment Income [Line Items]    
Amortized Cost 688,500  
Securities available for sale, at fair value 641,900  
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Net Investment Income [Line Items]    
Amortized Cost 444,100  
Securities available for sale, at fair value $ 400,900