Investment Securities - Amortized Cost and Estimated Fair Value by Contractual Maturity (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
AFS, Amortized Cost
Due in one year or less	$ 1,139
Due after one year through five years	8,868
Due after five years through ten years	1,729
Due after ten years	75,981
Debt Securities, Available-for-sale, Amortized Cost, Total	87,717	$ 155,088
AFS, Fair Value
Due in one year or less	1,125
Due after one year through five years	8,374
Due after five years through ten years	1,625
Due after ten years	68,154
Debt Securities, Available-for-sale, Total	79,278	153,123
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	60,081
Debt Securities, Held-to-Maturity, Amortized Cost, Total	60,081	1,494
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	53,905
Debt Securities, Held-to-Maturity, Fair Value	53,905	1,495
U.S. Treasury
AFS, Amortized Cost
Due in one year or less	1,120
Due after one year through five years	8,746
Due after five years through ten years	983
Due after ten years	6
Debt Securities, Available-for-sale, Amortized Cost, Total	10,855	9,892
AFS, Fair Value
Due in one year or less	1,106
Due after one year through five years	8,252
Due after five years through ten years	894
Due after ten years	6
Debt Securities, Available-for-sale, Total	10,258	9,795
GSE
AFS, Amortized Cost
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	269
Debt Securities, Available-for-sale, Amortized Cost, Total	269	1,667
AFS, Fair Value
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	250
Debt Securities, Available-for-sale, Total	250	1,698
Agency MBS
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date
Debt Securities, Held-to-Maturity, Amortized Cost, Total	60,081	1,494
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value
Debt Securities, Held-to-Maturity, Fair Value	53,905	1,495
Agency MBS | Agency MBS - residential
AFS, Amortized Cost
Due in one year or less	0
Due after one year through five years	1
Due after five years through ten years	587
Due after ten years	68,483
Debt Securities, Available-for-sale, Amortized Cost, Total	69,071	135,886
AFS, Fair Value
Due in one year or less	0
Due after one year through five years	1
Due after five years through ten years	573
Due after ten years	61,623
Debt Securities, Available-for-sale, Total	62,197	134,042
Agency MBS | Commercial Mortgage Backed Securities
AFS, Amortized Cost
Due in one year or less	0
Due after one year through five years	8
Due after five years through ten years	17
Due after ten years	2,941
Debt Securities, Available-for-sale, Amortized Cost, Total	2,966	2,928
AFS, Fair Value
Due in one year or less	0
Due after one year through five years	8
Due after five years through ten years	16
Due after ten years	2,630
Debt Securities, Available-for-sale, Total	2,654	2,882
States and political subdivisions
AFS, Amortized Cost
Due in one year or less	15
Due after one year through five years	76
Due after five years through ten years	124
Due after ten years	168
Debt Securities, Available-for-sale, Amortized Cost, Total	383	382
AFS, Fair Value
Due in one year or less	15
Due after one year through five years	76
Due after five years through ten years	125
Due after ten years	158
Debt Securities, Available-for-sale, Total	374	420
Non-agency MBS
AFS, Amortized Cost
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	4,050
Debt Securities, Available-for-sale, Amortized Cost, Total	4,050	4,305
AFS, Fair Value
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	3,425
Debt Securities, Available-for-sale, Total	3,425	4,258
Other
AFS, Amortized Cost
Due in one year or less	4
Due after one year through five years	37
Due after five years through ten years	18
Due after ten years	64
Debt Securities, Available-for-sale, Amortized Cost, Total	123	28
AFS, Fair Value
Due in one year or less	4
Due after one year through five years	37
Due after five years through ten years	17
Due after ten years	62
Debt Securities, Available-for-sale, Total	$ 120	$ 28