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INVESTMENT SECURITIES - Summary of Amortized Cost and Approximate Fair Value of Investment Securities (Detail) - USD ($)
Sep. 30, 2025
Dec. 31, 2024
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized Cost $ 801,324,000 $ 991,937,000
Allowance for Credit Losses 0 0
Net Carrying Value 801,324,000 991,937,000
Gross Unrealized Gains 947,000 2,349,000
Gross Unrealized Losses (45,141,000) (59,609,000)
Fair Value 757,130,000 934,677,000
Debt securities, held to maturity, accrued interest 1,800,000 2,400,000
Asset-backed securities    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized Cost 301,284,000 471,996,000
Allowance for Credit Losses 0 0
Net Carrying Value 301,284,000 471,996,000
Gross Unrealized Gains 942,000 1,775,000
Gross Unrealized Losses (1,551,000) (401,000)
Fair Value 300,675,000 473,370,000
Agency-guaranteed residential mortgage-backed securities    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized Cost 6,750,000 6,880,000
Allowance for Credit Losses 0 0
Net Carrying Value 6,750,000 6,880,000
Gross Unrealized Gains 0 0
Gross Unrealized Losses (740,000) (940,000)
Fair Value 6,010,000 5,940,000
Agency-guaranteed commercial mortgage-backed securities    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized Cost 1,708,000 1,770,000
Allowance for Credit Losses 0 0
Net Carrying Value 1,708,000 1,770,000
Gross Unrealized Gains 0 0
Gross Unrealized Losses (215,000) (146,000)
Fair Value 1,493,000 1,624,000
Agency-guaranteed residential collateralized mortgage obligations    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized Cost 157,231,000 169,754,000
Allowance for Credit Losses 0 0
Net Carrying Value 157,231,000 169,754,000
Gross Unrealized Gains 0 0
Gross Unrealized Losses (11,118,000) (21,984,000)
Fair Value 146,113,000 147,770,000
Agency-guaranteed commercial collateralized mortgage obligations    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized Cost 179,333,000 158,320,000
Allowance for Credit Losses 0 0
Net Carrying Value 179,333,000 158,320,000
Gross Unrealized Gains 0 0
Gross Unrealized Losses (21,968,000) (22,689,000)
Fair Value 157,365,000 135,631,000
Private label collateralized mortgage obligations    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized Cost 155,018,000 183,217,000
Allowance for Credit Losses 0 0
Net Carrying Value 155,018,000 183,217,000
Gross Unrealized Gains 5,000 574,000
Gross Unrealized Losses (9,549,000) (13,449,000)
Fair Value $ 145,474,000 $ 170,342,000