Investment Securities (Summary) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	$ 116,591	$ 130,798
Securities available for sale debt securities, unrealized gains	492	1,566
Securities available for sale debt securities, unrealized losses	(4,770)	(828)
Securities available for sale debt securities, fair value	112,313	131,536
Held to maturity securities, amortized cost	20,098	1,426
Held-to-maturity securities, unrealized gains	36	103
Held-to-maturity securities, unrealized losses	(19)	(7)
Held-to-maturity securities, fair value	20,115	1,522
Accrued interest	312	327
Debt securities, available-for-sale, allowance for credit loss	131	$ 130
Net unrealized losses, related to securities transferred to held to maturity	$ 1,300
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	99.00%	86.00%
U.S. Treasury and government agencies
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	$ 36,872	$ 46,210
Securities available for sale debt securities, unrealized gains	56	324
Securities available for sale debt securities, unrealized losses	(1,707)	(370)
Securities available for sale debt securities, fair value	35,221	46,164
Held to maturity securities, amortized cost	9,991	814
Held-to-maturity securities, unrealized gains	25	76
Held-to-maturity securities, unrealized losses	(5)
Held-to-maturity securities, fair value	10,011	890
Residential mortgage-backed \| Mortgage-backed Securities Agency
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	61,407	67,326
Securities available for sale debt securities, unrealized gains	91	695
Securities available for sale debt securities, unrealized losses	(2,683)	(389)
Securities available for sale debt securities, fair value	58,815	67,632
Held to maturity securities, amortized cost	9,548
Held-to-maturity securities, fair value	9,548
Residential mortgage-backed \| Mortgage-backed Securities Non-agency
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	1,132	927
Securities available for sale debt securities, unrealized gains	210	231
Securities available for sale debt securities, unrealized losses	(10)
Securities available for sale debt securities, fair value	1,332	1,158
Commercial mortgage-backed \| Mortgage-backed Securities Agency
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	2,152	1,740
Securities available for sale debt securities, unrealized gains	4	39
Securities available for sale debt securities, unrealized losses	(46)	(6)
Securities available for sale debt securities, fair value	2,110	1,773
Commercial mortgage-backed \| Mortgage-backed Securities Non-agency
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	3,504	3,423
Securities available for sale debt securities, unrealized gains	2	31
Securities available for sale debt securities, unrealized losses	(51)	(18)
Securities available for sale debt securities, fair value	3,455	3,436
Asset-backed
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	6,407	6,380
Securities available for sale debt securities, unrealized gains	46	60
Securities available for sale debt securities, unrealized losses	(148)	(31)
Securities available for sale debt securities, fair value	6,305	6,409
Other
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Securities available for sale debt securities, amortized cost	5,117	4,792
Securities available for sale debt securities, unrealized gains	83	186
Securities available for sale debt securities, unrealized losses	(125)	(14)
Securities available for sale debt securities, fair value	5,075	4,964
Held to maturity securities, amortized cost	559	612
Held-to-maturity securities, unrealized gains	11	27
Held-to-maturity securities, unrealized losses	(14)	(7)
Held-to-maturity securities, fair value	$ 556	$ 632

Debt Securities, Available-For-Sale And Held-To-Maturity, Accrued Interest, After Allowance for Credit Loss

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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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