Investment Securities (Gross Unrealized Loss and Fair Value of Securities Available for Sale Without an Allowance for Credit Losses) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months	$ (39)	$ (8)
Unrealized loss position less than 12 months	12,348	1,108
Unrealized loss position 12 months or more	(2,709)	(3,792)
Unrealized loss position 12 months or more	26,908	34,766
Total	(2,748)	(3,800)
Total	39,256	35,874
U.S. Treasury and government agencies
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months	(37)
Unrealized loss position less than 12 months	11,531
Unrealized loss position 12 months or more	(385)	(666)
Unrealized loss position 12 months or more	1,962	6,035
Total	(422)	(666)
Total	13,493	6,035
Residential mortgage-backed | Mortgage-backed Securities Agency
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months	(1)	(4)
Unrealized loss position less than 12 months	577	1,015
Unrealized loss position 12 months or more	(2,130)	(2,805)
Unrealized loss position 12 months or more	21,064	24,306
Total	(2,131)	(2,809)
Total	21,641	25,321
Residential mortgage-backed | Mortgage-backed Securities Non-agency
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	(3)	(4)
Unrealized loss position 12 months or more	52	84
Total	(3)	(5)
Total	52	99
Commercial mortgage servicing rights | Mortgage-backed Securities Agency
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months	(1)
Unrealized loss position less than 12 months	240
Unrealized loss position 12 months or more	(92)	(135)
Unrealized loss position 12 months or more	1,432	1,495
Total	(93)	(135)
Total	1,672	1,495
Commercial mortgage servicing rights | Mortgage-backed Securities Non-agency
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	(18)	(45)
Unrealized loss position 12 months or more	600	731
Total	(18)	(45)
Total	600	731
Asset-backed
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	(1)	(1)
Unrealized loss position 12 months or more	8	9
Total	(1)	(1)
Total	8	9
Other
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position less than 12 months		(3)
Unrealized loss position less than 12 months		78
Unrealized loss position 12 months or more	(80)	(136)
Unrealized loss position 12 months or more	1,790	2,106
Total	(80)	(139)
Total	$ 1,790	$ 2,184