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, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	$ (8)	$ (2,616)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	1,108	28,467
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(3,792)	(1,973)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	34,766	13,111
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(3,800)	(4,589)
Debt securities, available-for-sale, unrealized loss position - fair value	35,874	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, accumulated loss		(601)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value		5,868
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(666)	(235)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	6,035	2,208
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(666)	(836)
Debt securities, available-for-sale, unrealized loss position - fair value	6,035	8,076
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	(4)	(1,744)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	1,015	19,036
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(2,805)	(1,560)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	24,306	8,971
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(2,809)	(3,304)
Debt securities, available-for-sale, unrealized loss position - fair value	25,321	28,007
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	(1)	(6)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	15	112
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(4)	(2)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	84	17
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(5)	(8)
Debt securities, available-for-sale, unrealized loss position - fair value	99	129
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		(125)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value		1,283
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(135)	(45)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	1,495	372
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(135)	(170)
Debt securities, available-for-sale, unrealized loss position - fair value	1,495	1,655
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		(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, accumulated loss	(45)	(18)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	731	394
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(45)	(62)
Debt securities, available-for-sale, unrealized loss position - fair value	731	1,144
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated 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, accumulated loss	(1)	(1)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	9	5
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(1)	(1)
Debt securities, available-for-sale, unrealized loss position - fair value	9	5
Other debt
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(3)	(96)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	78	1,418
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(136)	(112)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	2,106	1,144
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(139)	(208)
Debt securities, available-for-sale, unrealized loss position - fair value	$ 2,184	$ 2,562