Investment Securities - Summary of Investment Securities (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt securities available for sale
Amortized Cost	$ 15,539	$ 11,295
Gross Unrealized Gain	89	39
Gross Unrealized Loss	805	932
Fair Value	14,823	10,402
Amortized cost of investment securities	3	3
Interest receivable	$ 56	$ 35
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Asset Pledged as Collateral
Debt securities available for sale
Fair Value	$ 14,500	$ 10,200
Mortgage-Related Debt Securities:
Debt securities available for sale
Amortized Cost	12,583	9,155
Gross Unrealized Gain	72	33
Gross Unrealized Loss	543	615
Fair Value	12,112	8,573
GSE CMOs
Debt securities available for sale
Amortized Cost	11,279	7,724
Gross Unrealized Gain	64	27
Gross Unrealized Loss	401	447
Fair Value	10,942	7,304
GSE certificates
Debt securities available for sale
Amortized Cost	1,151	1,273
Gross Unrealized Gain	1	0
Gross Unrealized Loss	141	167
Fair Value	1,011	1,106
Private label CMOs
Debt securities available for sale
Amortized Cost	153	158
Gross Unrealized Gain	7	6
Gross Unrealized Loss	1	1
Fair Value	159	163
Other Debt Securities:
Debt securities available for sale
Amortized Cost	2,956	2,140
Gross Unrealized Gain	17	6
Gross Unrealized Loss	262	317
Fair Value	2,711	1,829
GSE debentures
Debt securities available for sale
Amortized Cost	1,502	1,502
Gross Unrealized Gain	0	0
Gross Unrealized Loss	240	299
Fair Value	1,262	1,203
U. S. Treasury obligations
Debt securities available for sale
Amortized Cost	1,001
Gross Unrealized Gain	12
Gross Unrealized Loss	0
Fair Value	1,013
Asset-backed securities
Debt securities available for sale
Amortized Cost	227	237
Gross Unrealized Gain	0	1
Gross Unrealized Loss	5	2
Fair Value	222	236
Corporate bonds
Debt securities available for sale
Amortized Cost	174	314
Gross Unrealized Gain	0	0
Gross Unrealized Loss	7	6
Fair Value	167	308
Capital trust notes
Debt securities available for sale
Amortized Cost	47	47
Gross Unrealized Gain	5	5
Gross Unrealized Loss	10	10
Fair Value	42	42
Foreign notes
Debt securities available for sale
Amortized Cost		35
Gross Unrealized Gain		0
Gross Unrealized Loss		0
Fair Value		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

Debt Securities, Available For Sale, Excluding Interest And Equity Securities, Current

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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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