Investment Securities - Fair Value and Gross Unrealized Losses by Aging Category (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Available-for-sale securities
Less than 12 months, Fair value	$ 9,790	$ 12,133
Less than 12 months, Gross unrealized losses	49	57
12 months or more, Fair Value	1,520	4,694
12 months or more, Gross unrealized losses	13	49
Total fair value	11,310	16,827
Total gross unrealized losses	62	106
Total mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	297	3,768
Less than 12 months, Gross unrealized losses	4	25
12 months or more, Fair Value	389	391
12 months or more, Gross unrealized losses	6	17
Total fair value	686	4,159
Total gross unrealized losses	10	42
U.S. GSEs and government agencies
Available-for-sale securities
Total fair value	1,300	150
Residential: U.S.
Available-for-sale securities
Less than 12 months, Fair value	81	562
Less than 12 months, Gross unrealized losses	0	3
12 months or more, Fair Value	22	32
12 months or more, Gross unrealized losses	0	0
Total fair value	103	594
Total gross unrealized losses	0	3
Residential: Non-U.S.
Available-for-sale securities
Less than 12 months, Fair value	30	2,507
Less than 12 months, Gross unrealized losses	0	4
12 months or more, Fair Value	0	235
12 months or more, Gross unrealized losses	0	1
Total fair value	30	2,742
Total gross unrealized losses	0	5
Commercial
Available-for-sale securities
Less than 12 months, Fair value	186	699
Less than 12 months, Gross unrealized losses	4	18
12 months or more, Fair Value	367	124
12 months or more, Gross unrealized losses	6	16
Total fair value	553	823
Total gross unrealized losses	10	34
Obligations of U.S. states and municipalities
Available-for-sale securities
Less than 12 months, Fair value	102	49
Less than 12 months, Gross unrealized losses	2	1
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	102	49
Total gross unrealized losses	2	1
Non-U.S. government debt securities
Available-for-sale securities
Less than 12 months, Fair value	6,084	2,709
Less than 12 months, Gross unrealized losses	32	9
12 months or more, Fair Value	388	968
12 months or more, Gross unrealized losses	5	4
Total fair value	6,472	3,677
Total gross unrealized losses	37	13
Corporate debt securities
Available-for-sale securities
Less than 12 months, Fair value	57	91
Less than 12 months, Gross unrealized losses	7	3
12 months or more, Fair Value	42	5
12 months or more, Gross unrealized losses	0	0
Total fair value	99	96
Total gross unrealized losses	7	3
Asset-backed securities: Collateralized loan obligations
Available-for-sale securities
Less than 12 months, Fair value	3,227	5,248
Less than 12 months, Gross unrealized losses	4	18
12 months or more, Fair Value	354	2,645
12 months or more, Gross unrealized losses	0	13
Total fair value	3,581	7,893
Total gross unrealized losses	4	31
Asset-backed securities: Other
Available-for-sale securities
Less than 12 months, Fair value	23	268
Less than 12 months, Gross unrealized losses	0	1
12 months or more, Fair Value	347	685
12 months or more, Gross unrealized losses	2	15
Total fair value	370	953
Total gross unrealized losses	$ 2	$ 16