Investment Securities - Summary of Debt Securities Held-to-Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	$ 8,298,036	$ 8,444,362
Unrealized Gains	12,579	1,502
Unrealized Losses	(905,891)	(992,741)
Fair Value	7,404,724	7,453,123
Allowance for Credit Losses	(109)	(171)	$ (184)	$ (209)
Net Carrying Value	8,297,927	8,444,191
Held-to-maturity Securities
Financing Receivable, Credit Quality Indicator [Line Items]
Interest receivable	25,300	30,500
Agency CMO
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	19,079	19,847
Unrealized Gains	0	0
Unrealized Losses	(1,376)	(1,671)
Fair Value	17,703	18,176
Allowance for Credit Losses	0	0
Net Carrying Value	19,079	19,847
Agency MBS
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	3,036,457	3,109,411
Unrealized Gains	9,454	771
Unrealized Losses	(287,453)	(333,039)
Fair Value	2,758,458	2,777,143
Allowance for Credit Losses	0	0
Net Carrying Value	3,036,457	3,109,411
Agency CMBS
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	4,332,667	4,357,505
Unrealized Gains	2,909	414
Unrealized Losses	(560,390)	(613,914)
Fair Value	3,775,186	3,744,005
Allowance for Credit Losses	0	0
Net Carrying Value	4,332,667	4,357,505
Municipal bonds and notes
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	844,431	891,909
Unrealized Gains	216	317
Unrealized Losses	(53,782)	(40,266)
Fair Value	790,865	851,960
Allowance for Credit Losses	(109)	(171)
Net Carrying Value	844,322	891,738
CMBS
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	65,402	65,690
Unrealized Gains	0	0
Unrealized Losses	(2,890)	(3,851)
Fair Value	62,512	61,839
Allowance for Credit Losses	0	0
Net Carrying Value	$ 65,402	$ 65,690