Investment Securities - Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Available-for-sale securities
Less than 12 months, Fair value	$ 12,133	$ 18,608
Less than 12 months, Gross unrealized losses	57	49
12 months or more, Fair value	4,694	10,957
12 months or more, Gross unrealized losses	49	65
Total fair value	16,827	29,565
Total gross unrealized losses	106	114
Total mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	3,768	2,372
Less than 12 months, Gross unrealized losses	25	15
12 months or more, Fair value	391	1,042
12 months or more, Gross unrealized losses	17	5
Total fair value	4,159	3,414
Total gross unrealized losses	42	20
U.S. GSEs and government agencies
Available-for-sale securities
Total fair value	150	264
Residential: U.S.
Available-for-sale securities
Less than 12 months, Fair value	562	1,072
Less than 12 months, Gross unrealized losses	3	3
12 months or more, Fair value	32	423
12 months or more, Gross unrealized losses	0	3
Total fair value	594	1,495
Total gross unrealized losses	3	6
Residential: Non-U.S.
Available-for-sale securities
Less than 12 months, Fair value	2,507	13
Less than 12 months, Gross unrealized losses	4	0
12 months or more, Fair value	235	420
12 months or more, Gross unrealized losses	1	1
Total fair value	2,742	433
Total gross unrealized losses	5	1
Commercial
Available-for-sale securities
Less than 12 months, Fair value	699	1,287
Less than 12 months, Gross unrealized losses	18	12
12 months or more, Fair value	124	199
12 months or more, Gross unrealized losses	16	1
Total fair value	823	1,486
Total gross unrealized losses	34	13
Obligations of U.S. states and municipalities
Available-for-sale securities
Less than 12 months, Fair value	49	186
Less than 12 months, Gross unrealized losses	1	1
12 months or more, Fair value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	49	186
Total gross unrealized losses	1	1
Certificates of deposit
Available-for-sale securities
Less than 12 months, Fair value	0	77
Less than 12 months, Gross unrealized losses	0	0
12 months or more, Fair value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	0	77
Total gross unrealized losses	0	0
Non-U.S. government debt securities
Available-for-sale securities
Less than 12 months, Fair value	2,709	3,970
Less than 12 months, Gross unrealized losses	9	13
12 months or more, Fair value	968	1,406
12 months or more, Gross unrealized losses	4	4
Total fair value	3,677	5,376
Total gross unrealized losses	13	17
Corporate debt securities
Available-for-sale securities
Less than 12 months, Fair value	91	0
Less than 12 months, Gross unrealized losses	3	0
12 months or more, Fair value	5	0
12 months or more, Gross unrealized losses	0	0
Total fair value	96	0
Total gross unrealized losses	3	0
Asset-backed securities: Collateralized loan obligations
Available-for-sale securities
Less than 12 months, Fair value	5,248	10,364
Less than 12 months, Gross unrealized losses	18	11
12 months or more, Fair value	2,645	7,756
12 months or more, Gross unrealized losses	13	45
Total fair value	7,893	18,120
Total gross unrealized losses	31	56
Asset-backed securities: Other
Available-for-sale securities
Less than 12 months, Fair value	268	1,639
Less than 12 months, Gross unrealized losses	1	9
12 months or more, Fair value	685	753
12 months or more, Gross unrealized losses	15	11
Total fair value	953	2,392
Total gross unrealized losses	$ 16	$ 20