Investment Securities - Summary of Debt Securities Held-to-Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	$ 8,192,822		$ 8,444,362
Unrealized Gains	11,795		1,502
Unrealized Losses	(913,373)		(992,741)
Fair Value	7,291,244		7,453,123
Allowance for Credit Losses	(102)	$ (109)	(171)	$ (182)	$ (184)	$ (209)
Net Carrying Value	8,192,720		8,444,191
Held-to-maturity Securities
Financing Receivable, Credit Quality Indicator [Line Items]
Interest receivable	29,100		30,500
Agency CMO
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	18,246		19,847
Unrealized Gains	0		0
Unrealized Losses	(1,282)		(1,671)
Fair Value	16,964		18,176
Allowance for Credit Losses	0		0
Net Carrying Value	18,246		19,847
Agency MBS
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	2,954,301		3,109,411
Unrealized Gains	11,389		771
Unrealized Losses	(276,548)		(333,039)
Fair Value	2,689,142		2,777,143
Allowance for Credit Losses	0		0
Net Carrying Value	2,954,301		3,109,411
Agency CMBS
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	4,315,250		4,357,505
Unrealized Gains	149		414
Unrealized Losses	(569,802)		(613,914)
Fair Value	3,745,597		3,744,005
Allowance for Credit Losses	0		0
Net Carrying Value	4,315,250		4,357,505
Municipal bonds and notes
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	839,766		891,909
Unrealized Gains	257		317
Unrealized Losses	(63,392)		(40,266)
Fair Value	776,631		851,960
Allowance for Credit Losses	(102)		(171)
Net Carrying Value	839,664		891,738
CMBS
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	65,259		65,690
Unrealized Gains	0		0
Unrealized Losses	(2,349)		(3,851)
Fair Value	62,910		61,839
Allowance for Credit Losses	0		0
Net Carrying Value	$ 65,259		$ 65,690