Investment Securities (Gross Unrealized Loss and Fair Value of Securities Available for Sale Without an Allowance for Credit Losses) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	$ (25)	$ (8)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	3,362	1,108
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(4,134)	(3,792)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	33,465	34,766
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(4,159)	(3,800)
Debt securities, available-for-sale, unrealized loss position, fair value	36,827	35,874
U.S. Treasury and government agencies
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	(2)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	663
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(648)	(666)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	6,004	6,035
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(650)	(666)
Debt securities, available-for-sale, unrealized loss position, fair value	6,667	6,035
Residential mortgage-backed | Mortgage-backed Securities Agency
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	(18)	(4)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	1,965	1,015
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(3,165)	(2,805)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	23,252	24,306
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(3,183)	(2,809)
Debt securities, available-for-sale, unrealized loss position, fair value	25,217	25,321
Residential mortgage-backed | Mortgage-backed Securities Non-agency
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	(1)	(1)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	28	15
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(5)	(4)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	83	84
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(6)	(5)
Debt securities, available-for-sale, unrealized loss position, fair value	111	99
Commercial mortgage servicing rights | Mortgage-backed Securities Agency
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	(1)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	186
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(141)	(135)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	1,418	1,495
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(142)	(135)
Debt securities, available-for-sale, unrealized loss position, fair value	1,604	1,495
Commercial mortgage servicing rights | Mortgage-backed Securities Non-agency
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(32)	(45)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	691	731
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(32)	(45)
Debt securities, available-for-sale, unrealized loss position, fair value	691	731
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	(1)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	411
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(1)	(1)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	38	9
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(2)	(1)
Debt securities, available-for-sale, unrealized loss position, fair value	449	9
Other
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	(2)	(3)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	109	78
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(142)	(136)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	1,979	2,106
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(144)	(139)
Debt securities, available-for-sale, unrealized loss position, fair value	$ 2,088	$ 2,184