Investment Securities - Summary of Investment Securities (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Debt securities available-for-sale
Amortized Cost	$ 13,588	$ 11,295
Gross Unrealized Gain	66	39
Gross Unrealized Loss	835	932
Cumulative Amount of Fair Value Hedging Adjustment	7
Fair Value	12,826	10,402
Interest receivable	$ 40	$ 35
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Mortgage-Related Debt Securities:
Debt securities available-for-sale
Amortized Cost	$ 10,506	$ 9,155
Gross Unrealized Gain	61	33
Gross Unrealized Loss	551	615
Fair Value	10,016	8,573
GSE CMOs
Debt securities available-for-sale
Amortized Cost	9,096	7,724
Gross Unrealized Gain	53	27
Gross Unrealized Loss	405	447
Fair Value	8,744	7,304
GSE certificates
Debt securities available-for-sale
Amortized Cost	1,254	1,273
Gross Unrealized Gain	1	0
Gross Unrealized Loss	145	167
Fair Value	1,110	1,106
Private Label collateralized mortgage obligations
Debt securities available-for-sale
Amortized Cost	156	158
Gross Unrealized Gain	7	6
Gross Unrealized Loss	1	1
Fair Value	162	163
Other Debt Securities:
Debt securities available-for-sale
Amortized Cost	3,082	2,140
Gross Unrealized Gain	5	6
Gross Unrealized Loss	284	317
Cumulative Amount of Fair Value Hedging Adjustment	7
Fair Value	2,810	1,829
GSE debentures
Debt securities available-for-sale
Amortized Cost	1,502	1,502
Gross Unrealized Gain	0	0
Gross Unrealized Loss	261	299
Fair Value	1,241	1,203
U. S. Treasury obligations
Debt securities available-for-sale
Amortized Cost	1,002
Gross Unrealized Gain	0
Gross Unrealized Loss	1
Cumulative Amount of Fair Value Hedging Adjustment	7
Fair Value	1,008
Corporate bonds
Debt securities available-for-sale
Amortized Cost	259	314
Gross Unrealized Gain	0	0
Gross Unrealized Loss	10	6
Fair Value	249	308
Asset-backed securities
Debt securities available-for-sale
Amortized Cost	232	237
Gross Unrealized Gain	0	1
Gross Unrealized Loss	3	2
Fair Value	229	236
Capital trust notes
Debt securities available-for-sale
Amortized Cost	47	47
Gross Unrealized Gain	5	5
Gross Unrealized Loss	9	10
Fair Value	43	42
Foreign notes
Debt securities available-for-sale
Amortized Cost	35	35
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	35	35
Municipal bonds
Debt securities available-for-sale
Amortized Cost	5	5
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	$ 5	$ 5

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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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