Investment Securities (Summary) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	$ 130,798	$ 84,172
Securities available for sale debt securities, unrealized gains	1,566	3,302
Securities available for sale debt securities, unrealized losses	(828)	(116)
Securities available for sale debt securities, fair value	131,536	87,358
Held-to-maturity, debt securities	1,426	1,441
Held-to-maturity securities, unrealized gains	103	167
Held-to-maturity securities, unrealized losses	(7)	(3)
Held-to-maturity securities, fair value	1,522	1,605
Accrued interest, available-for-sale	322	238
Debt securities, available-for-sale, allowance for credit loss	$ 130	$ 79
Fitch, AAA OR AA Rating \| Credit Concentration Risk \| Held-to-maturity Securities
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Concentration risk, percentage	86.00%	85.00%
U.S. Treasury and government agencies
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	$ 46,210	$ 19,821
Securities available for sale debt securities, unrealized gains	324	903
Securities available for sale debt securities, unrealized losses	(370)	(13)
Securities available for sale debt securities, fair value	46,164	20,711
Held-to-maturity, debt securities	814	795
Held-to-maturity securities, unrealized gains	76	125
Held-to-maturity securities, fair value	890	920
Residential mortgage-backed Securities \| Mortgage-backed Securities Agency
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	67,326	47,355
Securities available for sale debt securities, unrealized gains	695	1,566
Securities available for sale debt securities, unrealized losses	(389)	(10)
Securities available for sale debt securities, fair value	67,632	48,911
Residential mortgage-backed Securities \| Mortgage-backed Securities Non-agency
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	927	1,272
Securities available for sale debt securities, unrealized gains	231	243
Securities available for sale debt securities, unrealized losses		(14)
Securities available for sale debt securities, fair value	1,158	1,501
Commercial Mortgage Backed Securities \| Mortgage-backed Securities Agency
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	1,740	2,571
Securities available for sale debt securities, unrealized gains	39	119
Securities available for sale debt securities, unrealized losses	(6)	(2)
Securities available for sale debt securities, fair value	1,773	2,688
Commercial Mortgage Backed Securities \| Mortgage-backed Securities Non-agency
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	3,423	3,678
Securities available for sale debt securities, unrealized gains	31	78
Securities available for sale debt securities, unrealized losses	(18)	(67)
Securities available for sale debt securities, fair value	3,436	3,689
Asset-backed Securities
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	6,380	5,060
Securities available for sale debt securities, unrealized gains	60	100
Securities available for sale debt securities, unrealized losses	(31)	(10)
Securities available for sale debt securities, fair value	6,409	5,150
Other debt
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	4,792	4,415
Securities available for sale debt securities, unrealized gains	186	293
Securities available for sale debt securities, unrealized losses	(14)
Securities available for sale debt securities, fair value	4,964	4,708
Held-to-maturity, debt securities	612	646
Held-to-maturity securities, unrealized gains	27	42
Held-to-maturity securities, unrealized losses	(7)	(3)
Held-to-maturity securities, fair value	$ 632	$ 685

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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