Investment Securities - Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
AFS securities:
Amortized Cost	$ 80,842	$ 84,056
Gross Unrealized Gains	14	15
Gross Unrealized Losses	11,891	12,270
AFS securities, Fair Value	68,965	71,801
HTM securities:
Amortized Cost	55,958	57,713
HTM securities, Fair Value	45,956	47,791
U.S. Treasury
AFS securities:
Amortized Cost	10,423	11,080
Gross Unrealized Gains	0	0
Gross Unrealized Losses	705	785
AFS securities, Fair Value	9,718	10,295
GSE
AFS securities:
Amortized Cost	325	339
Gross Unrealized Gains	0	0
Gross Unrealized Losses	37	36
AFS securities, Fair Value	288	303
Agency MBS - residential
AFS securities:
Amortized Cost	62,983	65,377
Gross Unrealized Gains	0	0
Gross Unrealized Losses	9,788	10,152
AFS securities, Fair Value	53,195	55,225
HTM securities:
Amortized Cost	55,958	57,713
Gross Unrealized Gains	0	0
Gross Unrealized Losses	10,002	9,922
HTM securities, Fair Value	45,956	47,791
Agency MBS - commercial
AFS securities:
Amortized Cost	2,843	2,887
Gross Unrealized Gains	0	0
Gross Unrealized Losses	551	463
AFS securities, Fair Value	2,292	2,424
States and political subdivisions
AFS securities:
Amortized Cost	425	425
Gross Unrealized Gains	14	15
Gross Unrealized Losses	21	24
AFS securities, Fair Value	418	416
Non-agency MBS
AFS securities:
Amortized Cost	3,817	3,927
Gross Unrealized Gains	0	0
Gross Unrealized Losses	789	810
AFS securities, Fair Value	3,028	3,117
Other
AFS securities:
Amortized Cost	26	21
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
AFS securities, Fair Value	$ 26	$ 21