Investment Securities - Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
AFS securities
Amortized Cost	$ 89,476	$ 155,088
Gross Unrealized Gains	58	755
Gross Unrealized Losses	4,781	2,720
AFS securities, Fair Value	84,753	153,123
HTM securities:
Amortized Cost	61,662	1,494
HTM securities, Fair Value	59,124	1,495
U.S. Treasury
AFS securities
Amortized Cost	9,891	9,892
Gross Unrealized Gains	0	9
Gross Unrealized Losses	479	106
AFS securities, Fair Value	9,412	9,795
GSE
AFS securities
Amortized Cost	257	1,667
Gross Unrealized Gains	0	33
Gross Unrealized Losses	12	2
AFS securities, Fair Value	245	1,698
Agency MBS
HTM securities:
Amortized Cost	61,662	1,494
Gross Unrealized Gains	0	1
Gross Unrealized Losses	2,538	0
HTM securities, Fair Value	59,124	1,495
Agency MBS \| Agency MBS - residential
AFS securities
Amortized Cost	71,956	135,886
Gross Unrealized Gains	37	656
Gross Unrealized Losses	3,755	2,500
AFS securities, Fair Value	68,238	134,042
Agency MBS \| Commercial Mortgage Backed Securities
AFS securities
Amortized Cost	2,831	2,928
Gross Unrealized Gains	2	18
Gross Unrealized Losses	174	64
AFS securities, Fair Value	2,659	2,882
States and political subdivisions
AFS securities
Amortized Cost	366	382
Gross Unrealized Gains	19	39
Gross Unrealized Losses	15	1
AFS securities, Fair Value	370	420
Non-agency MBS
AFS securities
Amortized Cost	4,149	4,305
Gross Unrealized Gains	0	0
Gross Unrealized Losses	346	47
AFS securities, Fair Value	3,803	4,258
Other
AFS securities
Amortized Cost	26	28
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
AFS securities, Fair Value	$ 26	$ 28

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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Amount, before tax, of unrealized loss 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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Amount of 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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Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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