Investment Securities (Gross Unrealized Loss and Fair Value of Securities Available for Sale Without an Allowance for Credit Losses) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months	$ (58)	$ (8)
Unrealized loss position less than 12 months	14,530	1,108
Unrealized loss position 12 months or more	(3,827)	(3,792)
Unrealized loss position 12 months or more	28,875	34,766
Total	(3,885)	(3,800)
Total	43,405	35,874
U.S. Treasury and government agencies
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months	(30)
Unrealized loss position less than 12 months	10,966
Unrealized loss position 12 months or more	(383)	(666)
Unrealized loss position 12 months or more	2,960	6,035
Total	(413)	(666)
Total	13,926	6,035
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months	(3)
Unrealized loss position less than 12 months	694
Unrealized loss position 12 months or more	(1)	(1)
Unrealized loss position 12 months or more	93	9
Total	(4)	(1)
Total	787	9
Other
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months	(1)	(3)
Unrealized loss position less than 12 months	105	78
Unrealized loss position 12 months or more	(139)	(136)
Unrealized loss position 12 months or more	1,932	2,106
Total	(140)	(139)
Total	2,037	2,184
Mortgage-backed Securities Agency | Residential mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months	(22)	(4)
Unrealized loss position less than 12 months	2,576	1,015
Unrealized loss position 12 months or more	(3,131)	(2,805)
Unrealized loss position 12 months or more	21,752	24,306
Total	(3,153)	(2,809)
Total	24,328	25,321
Mortgage-backed Securities Agency | Commercial mortgage servicing rights
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months	(2)
Unrealized loss position less than 12 months	189
Unrealized loss position 12 months or more	(139)	(135)
Unrealized loss position 12 months or more	1,397	1,495
Total	(141)	(135)
Total	1,586	1,495
Mortgage-backed Securities Non-agency | Residential mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months		(1)
Unrealized loss position less than 12 months		15
Unrealized loss position 12 months or more	(6)	(4)
Unrealized loss position 12 months or more	87	84
Total	(6)	(5)
Total	87	99
Mortgage-backed Securities Non-agency | Commercial mortgage servicing rights
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months
Unrealized loss position less than 12 months
Unrealized loss position 12 months or more	(28)	(45)
Unrealized loss position 12 months or more	654	731
Total	(28)	(45)
Total	$ 654	$ 731