Investment Securities - Summary of Amortized Cost and Approximate Fair Value of Investment Securities (Detail) - USD ($)	Mar. 31, 2023	Dec. 31, 2022
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	$ 870,294,000	$ 840,259,000
Allowance for Credit Losses	0	0
Net Carrying Value	870,294,000	840,259,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(33,581,000)	(46,446,000)
Fair Value	836,713,000	793,813,000
Debt securities, held to maturity, accrued interest	1,500,000	1,000,000
Asset-backed securities
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	322,877,000	361,107,000
Allowance for Credit Losses	0	0
Net Carrying Value	322,877,000	361,107,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(3,142,000)	(4,974,000)
Fair Value	319,735,000	356,133,000
Agency-guaranteed residential mortgage-backed securities
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	7,152,000	7,189,000
Allowance for Credit Losses	0	0
Net Carrying Value	7,152,000	7,189,000
Gross Unrealized Gains
Gross Unrealized Losses	(513,000)	(563,000)
Fair Value	6,639,000	6,626,000
Agency-guaranteed commercial mortgage-backed securities
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	1,909,000	1,928,000
Allowance for Credit Losses	0	0
Net Carrying Value	1,909,000	1,928,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(61,000)	(104,000)
Fair Value	1,848,000	1,824,000
Agency-guaranteed residential collateralized mortgage obligations
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	201,097,000	204,495,000
Allowance for Credit Losses	0	0
Net Carrying Value	201,097,000	204,495,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(13,136,000)	(18,376,000)
Fair Value	187,961,000	186,119,000
Agency-guaranteed commercial collateralized mortgage obligations
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	150,852,000	151,711,000
Allowance for Credit Losses	0	0
Net Carrying Value	150,852,000	151,711,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(7,239,000)	(9,435,000)
Fair Value	143,613,000	142,276,000
Private label collateralized mortgage obligations
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	186,407,000	113,829,000
Allowance for Credit Losses	0	0
Net Carrying Value	186,407,000	113,829,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(9,490,000)	(12,994,000)
Fair Value	$ 176,917,000	$ 100,835,000

Amount, after allowance for credit loss, of accrued interest on investment in debt security measured at amortized cost (held-to-maturity).

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