Investment Securities - Summary of Investment Securities (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Debt securities available-for-sale
Amortized Cost	$ 9,336
Equity securities:
Fair Value	14	$ 14
Total Securities
Amortized Cost	10,241	9,958
Gross Unrealized Gain	36	62
Gross Unrealized Loss	927	861
Fair Value	9,350	9,159
Amortized cost of investment securities	1
Interest receivable	$ 35	$ 38
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Mortgage Backed Securities And Other Securities
Debt securities available-for-sale
Amortized Cost	$ 10,225	$ 9,942
Gross Unrealized Gain	36	62
Gross Unrealized Loss	925	859
Fair Value	9,336	9,145
Mortgage-Related Debt Securities:
Debt securities available-for-sale
Amortized Cost	7,680	7,035
Gross Unrealized Gain	31	56
Gross Unrealized Loss	575	528
Fair Value	7,136	6,563
GSE certificates
Debt securities available-for-sale
Amortized Cost	1,342	1,366
Gross Unrealized Gain	1	1
Gross Unrealized Loss	163	146
Fair Value	1,180	1,221
GSE CMOs
Debt securities available-for-sale
Amortized Cost	6,167	5,495
Gross Unrealized Gain	25	48
Gross Unrealized Loss	412	381
Fair Value	5,780	5,162
Private Label CMOs
Debt securities available-for-sale
Amortized Cost	171	174
Gross Unrealized Gain	5	7
Gross Unrealized Loss	0	1
Fair Value	176	180
Other Debt Securities:
Debt securities available-for-sale
Amortized Cost	2,545	2,907
Gross Unrealized Gain	5	6
Gross Unrealized Loss	350	331
Fair Value	2,200	2,582
U. S. Treasury obligations
Debt securities available-for-sale
Amortized Cost	0	198
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	0	198
GSE debentures
Debt securities available-for-sale
Amortized Cost	1,752	1,899
Gross Unrealized Gain	0	1
Gross Unrealized Loss	312	291
Fair Value	1,440	1,609
Asset-backed securities
Debt securities available-for-sale
Amortized Cost	291	307
Gross Unrealized Gain	0	0
Gross Unrealized Loss	4	5
Fair Value	287	302
Municipal bonds
Debt securities available-for-sale
Amortized Cost	6	6
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	6	6
Corporate bonds
Debt securities available-for-sale
Amortized Cost	364	365
Gross Unrealized Gain	0	0
Gross Unrealized Loss	24	22
Fair Value	340	343
Foreign notes
Debt securities available-for-sale
Amortized Cost	35	35
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	1
Fair Value	35	34
Capital trust notes
Debt securities available-for-sale
Amortized Cost	97	97
Gross Unrealized Gain	5	5
Gross Unrealized Loss	10	12
Fair Value	92	90
Equity securities:
Equity securities:
Amortized Cost	16	16
Gross Unrealized Loss	2	2
Fair Value	14	14
Mutual funds and common stock
Equity securities:
Amortized Cost	16	16
Gross Unrealized Loss	2	2
Fair Value	$ 14	$ 14

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