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, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	$ (4,289)	$ (790)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	88,425	80,895
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(453)	(26)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	6,990	2,211
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(4,742)	(816)
Debt securities, available-for-sale, unrealized loss position, fair value	95,415	83,106
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	(1,433)	(370)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	26,147	32,600
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(274)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	3,788
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(1,707)	(370)
Debt securities, available-for-sale, unrealized loss position, fair value	29,935	32,600
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	(2,551)	(369)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	50,802	41,521
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(132)	(20)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	1,940	1,489
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(2,683)	(389)
Debt securities, available-for-sale, unrealized loss position, fair value	52,742	43,010
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	(9)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	334
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(1)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	20
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(10)
Debt securities, available-for-sale, unrealized loss position, fair value	354
Commercial 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	(42)	(5)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	1,481	451
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(4)	(1)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	120	60
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(46)	(6)
Debt securities, available-for-sale, unrealized loss position, fair value	1,601	511
Commercial 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	(31)	(4)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	2,246	1,453
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(6)	(3)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	470	474
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(37)	(7)
Debt securities, available-for-sale, unrealized loss position, fair value	2,716	1,927
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	(123)	(29)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	5,091	3,465
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(25)	(2)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	517	188
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(148)	(31)
Debt securities, available-for-sale, unrealized loss position, fair value	5,608	3,653
Other
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, unrealized loss	(100)	(13)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	2,324	1,405
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, unrealized loss	(11)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	135
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(111)	(13)
Debt securities, available-for-sale, unrealized loss position, fair value	$ 2,459	$ 1,405