Investment Securities (Gross Unrealized Loss and Fair Value of Securities Available for Sale Without an Allowance for Credit Losses) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	$ (790)	$ (42)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	80,895	5,185
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(26)	(27)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	2,211	1,724
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(816)	(69)
Debt securities, available-for-sale, unrealized loss position	83,106	6,909
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, accumulated loss	(370)	(13)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	32,600	603
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(370)	(13)
Debt securities, available-for-sale, unrealized loss position	32,600	603
Residential mortgage-backed Securities | Mortgage-backed Securities Agency
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(369)	(8)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	41,521	3,152
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(20)	(2)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	1,489	82
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(389)	(10)
Debt securities, available-for-sale, unrealized loss position	43,010	3,234
Residential mortgage-backed Securities | 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, accumulated loss		(7)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value		119
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss		(7)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value		73
Debt securities, available-for-sale, unrealized loss position, accumulated loss		(14)
Debt securities, available-for-sale, unrealized loss position		192
Commercial Mortgage Backed Securities | Mortgage-backed Securities Agency
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(5)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	451
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(1)	(2)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	60	149
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(6)	(2)
Debt securities, available-for-sale, unrealized loss position	511	149
Commercial Mortgage Backed Securities | 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, accumulated loss	(4)	(13)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	1,453	972
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(3)	(7)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	474	714
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(7)	(20)
Debt securities, available-for-sale, unrealized loss position	1,927	1,686
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(29)	(1)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	3,465	339
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(2)	(9)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	188	706
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(31)	(10)
Debt securities, available-for-sale, unrealized loss position	3,653	$ 1,045
Other debt
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(13)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	1,405
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(13)
Debt securities, available-for-sale, unrealized loss position	$ 1,405