Investment Securities - Fair Value and Gross Unrealized Losses on Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Fair Value
Less than 12 months	$ 14,913	$ 41,346
12 months or more	32,597	8,190
Total	47,510	49,536
Unrealized Losses
Less than 12 months	(1,273)	(4,295)
12 months or more	(4,803)	(1,751)
Total	(6,076)	(6,046)
U.S. Treasury and federal agencies securities
Fair Value
Less than 12 months	654	2,400
12 months or more	1,686	0
Total	2,340	2,400
Unrealized Losses
Less than 12 months	(24)	(188)
12 months or more	(160)	0
Total	(184)	(188)
Obligations of states and political subdivisions securities
Fair Value
Less than 12 months		0
12 months or more		1
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	2,728	10,078
12 months or more	7,853	938
Total	10,581	11,016
Unrealized Losses
Less than 12 months	(213)	(1,170)
12 months or more	(1,165)	(202)
Total	(1,378)	(1,372)
Agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	10,132	22,083
12 months or more	15,171	3,697
Total	25,303	25,780
Unrealized Losses
Less than 12 months	(961)	(2,487)
12 months or more	(2,620)	(1,026)
Total	(3,581)	(3,513)
Non-agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	529	3,621
12 months or more	3,845	1,059
Total	4,374	4,680
Unrealized Losses
Less than 12 months	(30)	(272)
12 months or more	(508)	(248)
Total	(538)	(520)
Asset-backed securities and other debt securities
Fair Value
Less than 12 months	870	3,164
12 months or more	4,042	2,495
Total	4,912	5,659
Unrealized Losses
Less than 12 months	(45)	(178)
12 months or more	(350)	(275)
Total	$ (395)	$ (453)