INVESTMENT SECURITIES - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	$ 308,178	$ 618,574
Less than 12 Months, Unrealized Losses	(3,548)	(11,103)
12 Months or More, Fair Value	676,096	974,040
12 Months or More, Unrealized Losses	(32,419)	(56,938)
Total, Fair Value	984,274	1,592,614
Total, Unrealized Losses	(35,967)	(68,041)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	0
Less than 12 Months, Unrealized Losses	0
12 Months or More, Fair Value	81,699
12 Months or More, Unrealized Losses	(20)
Total, Fair Value	81,699
Total, Unrealized Losses	(20)
Agency-guaranteed residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	20,022	266,568
Less than 12 Months, Unrealized Losses	(140)	(3,745)
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Total, Fair Value	20,022	266,568
Total, Unrealized Losses	(140)	(3,745)
Agency-guaranteed residential collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	230,892	126,602
Less than 12 Months, Unrealized Losses	(1,715)	(2,717)
12 Months or More, Fair Value	95,096	100,144
12 Months or More, Unrealized Losses	(6,891)	(13,395)
Total, Fair Value	325,988	226,746
Total, Unrealized Losses	(8,606)	(16,112)
Agency-guaranteed commercial collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	10,157	85,902
Less than 12 Months, Unrealized Losses	(49)	(2,819)
12 Months or More, Fair Value	65,250	0
12 Months or More, Unrealized Losses	(2,362)	0
Total, Fair Value	75,407	85,902
Total, Unrealized Losses	(2,411)	(2,819)
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	0	35,710
Less than 12 Months, Unrealized Losses	0	(265)
12 Months or More, Fair Value	10,660	205,639
12 Months or More, Unrealized Losses	(149)	(1,928)
Total, Fair Value	10,660	241,349
Total, Unrealized Losses	(149)	(2,193)
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value		0
Less than 12 Months, Unrealized Losses		0
12 Months or More, Fair Value		77,708
12 Months or More, Unrealized Losses		(999)
Total, Fair Value		77,708
Total, Unrealized Losses		(999)
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	17,198	74,373
Less than 12 Months, Unrealized Losses	(1,552)	(976)
12 Months or More, Fair Value	86,888	239,509
12 Months or More, Unrealized Losses	(6,112)	(16,064)
Total, Fair Value	104,086	313,882
Total, Unrealized Losses	(7,664)	(17,040)
Private label collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	29,909	29,419
Less than 12 Months, Unrealized Losses	(92)	(581)
12 Months or More, Fair Value	336,503	351,040
12 Months or More, Unrealized Losses	(16,885)	(24,552)
Total, Fair Value	366,412	380,459
Total, Unrealized Losses	$ (16,977)	$ (25,133)