Investment Securities - Fair Value and Gross Unrealized Losses on Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Fair Value
Less than 12 months	$ 45,821	$ 7,743
12 months or more	4,132	952
Total	49,953	8,695
Unrealized Losses
Less than 12 months	(5,193)	(106)
12 months or more	(896)	(38)
Total	(6,089)	(144)
U.S. Treasury and federal agencies securities
Fair Value
Less than 12 months	2,377
12 months or more	0
Total	2,377
Unrealized Losses
Less than 12 months	(204)
12 months or more	0
Total	(204)
Obligations of states and political subdivisions securities
Fair Value
Less than 12 months	1
12 months or more	0
Total	1
Unrealized Losses
Less than 12 months	0
12 months or more	0
Total	0
Agency mortgage-backed securities | Residential mortgage backed securities
Fair Value
Less than 12 months	10,719	935
12 months or more	509	161
Total	11,228	1,096
Unrealized Losses
Less than 12 months	(1,231)	(10)
12 months or more	(110)	(8)
Total	(1,341)	(18)
Agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	24,048	2,886
12 months or more	1,806	424
Total	25,854	3,310
Unrealized Losses
Less than 12 months	(3,020)	(49)
12 months or more	(532)	(20)
Total	(3,552)	(69)
Non-agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	4,155	1,052
12 months or more	485	0
Total	4,640	1,052
Unrealized Losses
Less than 12 months	(421)	(13)
12 months or more	(127)	0
Total	(548)	(13)
Asset-backed securities and other debt securities
Fair Value
Less than 12 months	4,521	2,870
12 months or more	1,332	367
Total	5,853	3,237
Unrealized Losses
Less than 12 months	(317)	(34)
12 months or more	(127)	(10)
Total	$ (444)	$ (44)