Investment Securities - Fair Value and Gross Unrealized Losses on Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Fair Value
Less than 12 months	$ 32,621	$ 7,743
12 months or more	1,470	952
Total	34,091	8,695
Unrealized Losses
Less than 12 months	(1,388)	(106)
12 months or more	(131)	(38)
Total	(1,519)	(144)
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
U.S. Treasury and federal agencies securities
Fair Value
Less than 12 months	1,688
12 months or more	0
Total	1,688
Unrealized Losses
Less than 12 months	(41)
12 months or more	0
Total	(41)
Agency mortgage-backed securities | Residential mortgage backed securities
Fair Value
Less than 12 months	7,613	935
12 months or more	153	161
Total	7,766	1,096
Unrealized Losses
Less than 12 months	(197)	(10)
12 months or more	(18)	(8)
Total	(215)	(18)
Agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	14,945	2,886
12 months or more	858	424
Total	15,803	3,310
Unrealized Losses
Less than 12 months	(798)	(49)
12 months or more	(98)	(20)
Total	(896)	(69)
Non-agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	3,994	1,052
12 months or more	0	0
Total	3,994	1,052
Unrealized Losses
Less than 12 months	(161)	(13)
12 months or more	0	0
Total	(161)	(13)
Asset-backed securities and other debt securities
Fair Value
Less than 12 months	4,380	2,870
12 months or more	459	367
Total	4,839	3,237
Unrealized Losses
Less than 12 months	(191)	(34)
12 months or more	(15)	(10)
Total	$ (206)	$ (44)