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Investment Securities - Summary of Debt Securities Held-to-Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	$ 7,969,672	$ 8,444,362
Gross Unrealized Gains	25,062	1,502
Gross Unrealized Losses	(826,151)	(992,741)
Fair Value	7,168,583	7,453,123
Allowance for Credit Losses	(97)	(171)	$ (209)	$ (182)
Net Carrying Value	7,969,575	8,444,191
Held-to-maturity Securities
Financing Receivable, Credit Quality Indicator [Line Items]
Interest receivable	28,100	30,500
Agency CMO
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	16,791	19,847
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,071)	(1,671)
Fair Value	15,720	18,176
Allowance for Credit Losses	0	0
Net Carrying Value	16,791	19,847
Agency MBS
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	2,767,869	3,109,411
Gross Unrealized Gains	24,073	771
Gross Unrealized Losses	(226,089)	(333,039)
Fair Value	2,565,853	2,777,143
Allowance for Credit Losses	0	0
Net Carrying Value	2,767,869	3,109,411
Agency CMBS
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	4,295,308	4,357,505
Gross Unrealized Gains	0	414
Gross Unrealized Losses	(567,040)	(613,914)
Fair Value	3,728,268	3,744,005
Allowance for Credit Losses	0	0
Net Carrying Value	4,295,308	4,357,505
Municipal bonds and notes
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	824,734	891,909
Gross Unrealized Gains	989	317
Gross Unrealized Losses	(30,461)	(40,266)
Fair Value	795,262	851,960
Allowance for Credit Losses	(97)	(171)
Net Carrying Value	824,637	891,738
CMBS
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost	64,970	65,690
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,490)	(3,851)
Fair Value	63,480	61,839
Allowance for Credit Losses	0	0
Net Carrying Value	$ 64,970	$ 65,690

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