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, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	$ (126)	$ (2,616)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	4,653	28,467
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(5,412)	(1,973)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	34,079	13,111
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(5,538)	(4,589)
Debt securities, available-for-sale, unrealized loss position, fair value	38,732	41,578
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	(3)	(601)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	374	5,868
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(778)	(235)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	6,013	2,208
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(781)	(836)
Debt securities, available-for-sale, unrealized loss position, fair value	6,387	8,076
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	(107)	(1,744)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	3,294	19,036
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(4,171)	(1,560)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	23,547	8,971
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(4,278)	(3,304)
Debt securities, available-for-sale, unrealized loss position, fair value	26,841	28,007
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)	(6)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	51	112
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(6)	(2)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	71	17
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(7)	(8)
Debt securities, available-for-sale, unrealized loss position, fair value	122	129
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)	(125)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	42	1,283
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(193)	(45)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	1,493	372
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(194)	(170)
Debt securities, available-for-sale, unrealized loss position, fair value	1,535	1,655
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		(44)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value		750
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(55)	(18)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	793	394
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(55)	(62)
Debt securities, available-for-sale, unrealized loss position, fair value	793	1,144
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	(6)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	687
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	10	5
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(7)	(1)
Debt securities, available-for-sale, unrealized loss position, fair value	697	5
Other
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	(8)	(96)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	205	1,418
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(208)	(112)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	2,152	1,144
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(216)	(208)
Debt securities, available-for-sale, unrealized loss position, fair value	$ 2,357	$ 2,562