Securities - Fair Value of Investments with Continuous Unrealized Loss Position (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Available-for-sale:
Less than 12 months, Fair value	$ 33,275,000,000	$ 12,855,000,000
Less than 12 months, Unrealized losses	458,000,000	47,000,000
12 months or more, Fair value	2,562,000,000	3,668,000,000
12 months or more, Unrealized losses	49,000,000	61,000,000
Total, Fair value	35,837,000,000	16,523,000,000
Total, Unrealized losses	507,000,000	108,000,000
Debt securities, available-for-sale, unrealized loss position	35,837,000,000	16,523,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	507,000,000	108,000,000
AOCI, transfers from AFS to HTM Securities, gross unrealized losses, less than 12 months	49,000,000	0
AOCI, transfers from AFS to HTM Securities, gross unrealized losses, greater than 12 months	31,000,000	44,000,000
Grantor Trust
Available-for-sale:
Total, Fair value	8,700,000,000	1,600,000,000
Total, Unrealized losses	1,000,000	1,000,000
Debt securities, available-for-sale, unrealized loss position	8,700,000,000	1,600,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	1,000,000	1,000,000
Agency residential mortgage-backed securities (“RMBS”)
Available-for-sale:
Less than 12 months, Fair value	2,830,000,000	850,000,000
Less than 12 months, Unrealized losses	16,000,000	4,000,000
12 months or more, Fair value	491,000,000	1,965,000,000
12 months or more, Unrealized losses	31,000,000	47,000,000
Total, Fair value	3,321,000,000	2,815,000,000
Total, Unrealized losses	47,000,000	51,000,000
Debt securities, available-for-sale, unrealized loss position	3,321,000,000	2,815,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	47,000,000	51,000,000
U.S. Treasury
Available-for-sale:
Less than 12 months, Fair value	12,106,000,000	4,253,000,000
Less than 12 months, Unrealized losses	222,000,000	21,000,000
12 months or more, Fair value	46,000,000	0
12 months or more, Unrealized losses	4,000,000	0
Total, Fair value	12,152,000,000	4,253,000,000
Total, Unrealized losses	226,000,000	21,000,000
Debt securities, available-for-sale, unrealized loss position	12,152,000,000	4,253,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	226,000,000	21,000,000
Sovereign debt/sovereign guaranteed
Available-for-sale:
Less than 12 months, Fair value	3,921,000,000	1,349,000,000
Less than 12 months, Unrealized losses	42,000,000	1,000,000
12 months or more, Fair value	104,000,000	135,000,000
12 months or more, Unrealized losses	0	0
Total, Fair value	4,025,000,000	1,484,000,000
Total, Unrealized losses	42,000,000	1,000,000
Debt securities, available-for-sale, unrealized loss position	4,025,000,000	1,484,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	42,000,000	1,000,000
Agency commercial mortgage-backed securities (“MBS”)
Available-for-sale:
Less than 12 months, Fair value	1,945,000,000	440,000,000
Less than 12 months, Unrealized losses	24,000,000	1,000,000
12 months or more, Fair value	561,000,000	266,000,000
12 months or more, Unrealized losses	1,000,000	1,000,000
Total, Fair value	2,506,000,000	706,000,000
Total, Unrealized losses	25,000,000	2,000,000
Debt securities, available-for-sale, unrealized loss position	2,506,000,000	706,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	25,000,000	2,000,000
Foreign covered bonds
Available-for-sale:
Less than 12 months, Fair value	1,637,000,000	468,000,000
Less than 12 months, Unrealized losses	9,000,000	1,000,000
12 months or more, Fair value	93,000,000	90,000,000
12 months or more, Unrealized losses	0	0
Total, Fair value	1,730,000,000	558,000,000
Total, Unrealized losses	9,000,000	1,000,000
Debt securities, available-for-sale, unrealized loss position	1,730,000,000	558,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	9,000,000	1,000,000
Supranational
Available-for-sale:
Less than 12 months, Fair value	2,357,000,000	1,041,000,000
Less than 12 months, Unrealized losses	23,000,000	1,000,000
12 months or more, Fair value	268,000,000	132,000,000
12 months or more, Unrealized losses	3,000,000	0
Total, Fair value	2,625,000,000	1,173,000,000
Total, Unrealized losses	26,000,000	1,000,000
Debt securities, available-for-sale, unrealized loss position	2,625,000,000	1,173,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	26,000,000	1,000,000
Collateralized loan obligations (“CLOs”)
Available-for-sale:
Less than 12 months, Fair value	422,000,000	1,849,000,000
Less than 12 months, Unrealized losses	1,000,000	6,000,000
12 months or more, Fair value	337,000,000	579,000,000
12 months or more, Unrealized losses	2,000,000	4,000,000
Total, Fair value	759,000,000	2,428,000,000
Total, Unrealized losses	3,000,000	10,000,000
Debt securities, available-for-sale, unrealized loss position	759,000,000	2,428,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	3,000,000	10,000,000
Foreign government agencies
Available-for-sale:
Less than 12 months, Fair value	947,000,000
Less than 12 months, Unrealized losses	7,000,000
12 months or more, Fair value	42,000,000
12 months or more, Unrealized losses	0
Total, Fair value	989,000,000
Total, Unrealized losses	7,000,000
Debt securities, available-for-sale, unrealized loss position	989,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	7,000,000
U.S. government agencies
Available-for-sale:
Less than 12 months, Fair value	904,000,000	160,000,000
Less than 12 months, Unrealized losses	13,000,000	1,000,000
12 months or more, Fair value	0	0
12 months or more, Unrealized losses	0	0
Total, Fair value	904,000,000	160,000,000
Total, Unrealized losses	13,000,000	1,000,000
Debt securities, available-for-sale, unrealized loss position	904,000,000	160,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	13,000,000	1,000,000
Other asset-backed securities (“ABS”)
Available-for-sale:
Less than 12 months, Fair value	1,066,000,000	449,000,000
Less than 12 months, Unrealized losses	8,000,000	2,000,000
12 months or more, Fair value	144,000,000	226,000,000
12 months or more, Unrealized losses	1,000,000	1,000,000
Total, Fair value	1,210,000,000	675,000,000
Total, Unrealized losses	9,000,000	3,000,000
Debt securities, available-for-sale, unrealized loss position	1,210,000,000	675,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	9,000,000	3,000,000
Non-agency commercial MBS
Available-for-sale:
Less than 12 months, Fair value	766,000,000	468,000,000
Less than 12 months, Unrealized losses	13,000,000	4,000,000
12 months or more, Fair value	137,000,000	170,000,000
12 months or more, Unrealized losses	3,000,000	2,000,000
Total, Fair value	903,000,000	638,000,000
Total, Unrealized losses	16,000,000	6,000,000
Debt securities, available-for-sale, unrealized loss position	903,000,000	638,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	16,000,000	6,000,000
Non-agency RMBS
Available-for-sale:
Less than 12 months, Fair value	1,190,000,000	973,000,000
Less than 12 months, Unrealized losses	11,000,000	3,000,000
12 months or more, Fair value	318,000,000	103,000,000
12 months or more, Unrealized losses	4,000,000	6,000,000
Total, Fair value	1,508,000,000	1,076,000,000
Total, Unrealized losses	15,000,000	9,000,000
Debt securities, available-for-sale, unrealized loss position	1,508,000,000	1,076,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	15,000,000	9,000,000
Non-agency RMBS | Grantor Trust
Available-for-sale:
Less than 12 months, Fair value	1,000,000	16,000,000
Less than 12 months, Unrealized losses	1,000,000	1,000,000
12 months or more, Fair value	2,000,000	2,000,000
12 months or more, Unrealized losses	1,000,000	1,000,000
State and political subdivisions
Available-for-sale:
Less than 12 months, Fair value	1,607,000,000	273,000,000
Less than 12 months, Unrealized losses	22,000,000	1,000,000
12 months or more, Fair value	21,000,000	2,000,000
12 months or more, Unrealized losses	0	0
Total, Fair value	1,628,000,000	275,000,000
Total, Unrealized losses	22,000,000	1,000,000
Debt securities, available-for-sale, unrealized loss position	1,628,000,000	275,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	22,000,000	1,000,000
Corporate bonds
Available-for-sale:
Less than 12 months, Fair value	1,577,000,000	282,000,000
Less than 12 months, Unrealized losses	47,000,000	1,000,000
12 months or more, Fair value	0	0
12 months or more, Unrealized losses	0	0
Total, Fair value	1,577,000,000	282,000,000
Total, Unrealized losses	47,000,000	1,000,000
Debt securities, available-for-sale, unrealized loss position	1,577,000,000	282,000,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	$ 47,000,000	$ 1,000,000