Investment Securities (Available-For-Sale Securities by Major Security Type) (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss	$ 39,178	$ 35,778
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Accrued interest receivable	Accrued interest receivable
Total, Amortized Cost	$ 14,299,825	$ 13,197,724
Gross Unrecognized Gains	25,853	31,467
Gross Unrecognized Losses	(207,101)	(171,572)
Fair Value	14,118,577	13,057,619
U.S. Treasury obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Total, Amortized Cost	3,396,987	3,313,012
Gross Unrecognized Gains	0	6
Gross Unrecognized Losses	(95,075)	(75,795)
Fair Value	3,301,912	3,237,223
State or local housing agency obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Total, Amortized Cost	48,210	24,465
Gross Unrecognized Gains	41	0
Gross Unrecognized Losses	(13)	(286)
Fair Value	48,238	24,179
Non-mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Total, Amortized Cost	3,445,197	3,337,477
Gross Unrecognized Gains	41	6
Gross Unrecognized Losses	(95,088)	(76,081)
Fair Value	3,350,150	3,261,402
U.S. obligation MBS [Member]
Debt Securities, Available-for-sale [Line Items]
Total, Amortized Cost	68,509	78,046
Gross Unrecognized Gains	0	0
Gross Unrecognized Losses	(1,022)	(783)
Fair Value	67,487	77,263
GSE MBS [Member]
Debt Securities, Available-for-sale [Line Items]
Total, Amortized Cost	10,786,119	9,782,201
Gross Unrecognized Gains	25,812	31,461
Gross Unrecognized Losses	(110,991)	(94,708)
Fair Value	10,700,940	9,718,954
Mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Total, Amortized Cost	10,854,628	9,860,247
Gross Unrecognized Gains	25,812	31,461
Gross Unrecognized Losses	(112,013)	(95,491)
Fair Value	$ 10,768,427	$ 9,796,217

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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