INVESTMENT SECURITIES - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	$ 317,303	$ 356,234
Less than 12 Months, Unrealized Losses	(5,035)	(12,782)
12 Months or More, Fair Value	1,374,196	1,778,899
12 Months or More, Unrealized Losses	(75,097)	(116,764)
Total, Fair Value	1,691,499	2,135,133
Total, Unrealized Losses	(80,132)	(129,546)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	0	0
Less than 12 Months, Unrealized Losses	0	0
12 Months or More, Fair Value	30,960	64,029
12 Months or More, Unrealized Losses	(1,241)	(4,027)
Total, Fair Value	30,960	64,029
Total, Unrealized Losses	(1,241)	(4,027)
Agency-guaranteed residential collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	0	0
Less than 12 Months, Unrealized Losses	0	0
12 Months or More, Fair Value	109,456	116,908
12 Months or More, Unrealized Losses	(7,933)	(12,681)
Total, Fair Value	109,456	116,908
Total, Unrealized Losses	(7,933)	(12,681)
Agency-guaranteed commercial collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	45,080
Less than 12 Months, Unrealized Losses	(618)
12 Months or More, Fair Value	0
12 Months or More, Unrealized Losses	0
Total, Fair Value	45,080
Total, Unrealized Losses	(618)
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	37,164	29,241
Less than 12 Months, Unrealized Losses	(284)	(392)
12 Months or More, Fair Value	250,635	438,551
12 Months or More, Unrealized Losses	(4,483)	(10,626)
Total, Fair Value	287,799	467,792
Total, Unrealized Losses	(4,767)	(11,018)
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	0	0
Less than 12 Months, Unrealized Losses	0	0
12 Months or More, Fair Value	77,074	121,636
12 Months or More, Unrealized Losses	(1,637)	(4,249)
Total, Fair Value	77,074	121,636
Total, Unrealized Losses	(1,637)	(4,249)
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	59,408	23,243
Less than 12 Months, Unrealized Losses	(766)	(1,147)
12 Months or More, Fair Value	319,371	424,768
12 Months or More, Unrealized Losses	(26,637)	(33,764)
Total, Fair Value	378,779	448,011
Total, Unrealized Losses	(27,403)	(34,911)
Private label collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	175,651	303,750
Less than 12 Months, Unrealized Losses	(3,367)	(11,243)
12 Months or More, Fair Value	586,700	613,007
12 Months or More, Unrealized Losses	(33,166)	(51,417)
Total, Fair Value	762,351	916,757
Total, Unrealized Losses	$ (36,533)	$ (62,660)