Investment Securities (Summary) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	$ 93,661	$ 67,790
Securities available for sale debt securities, unrealized gains	3,613	1,471
Securities available for sale debt securities, unrealized losses	(222)	(98)
Investment securities – available for sale	97,052	69,163
Held to maturity securities, amortized cost	1,441	17,661
Held-to-maturity securities, unrealized gains	188	423
Held-to-maturity securities, unrealized losses	(14)	(40)
Held-to-maturity securities, fair value	1,615	18,044
Debt securities, available-for-sale, accrued interest	270
Debt securities, held-to-maturity, accrued interest	5
Debt securities, available-for-sale, allowance for credit loss	30
Debt securities, held-to-maturity, allowance for credit loss	$ 2
Credit Concentration Risk [Member] | Fitch, AAA or AA Rating [Member]
Debt Securities, Held-to-maturity [Abstract]
Concentration risk, percentage	84.00%
US Treasury and Government [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	$ 19,255	16,150
Securities available for sale debt securities, unrealized gains	933	382
Securities available for sale debt securities, unrealized losses		(16)
Investment securities – available for sale	20,188	16,516
Held to maturity securities, amortized cost	785	776
Held-to-maturity securities, unrealized gains	146	56
Held-to-maturity securities, fair value	931	832
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Agency [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	55,630	35,847
Securities available for sale debt securities, unrealized gains	1,860	517
Securities available for sale debt securities, unrealized losses	(10)	(43)
Investment securities – available for sale	57,480	36,321
Held to maturity securities, amortized cost		14,419
Held-to-maturity securities, unrealized gains		270
Held-to-maturity securities, unrealized losses		(26)
Held-to-maturity securities, fair value		14,663
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	1,472	1,515
Securities available for sale debt securities, unrealized gains	225	302
Securities available for sale debt securities, unrealized losses	(15)	(3)
Investment securities – available for sale	1,682	1,814
Held to maturity securities, amortized cost		133
Held-to-maturity securities, unrealized gains		7
Held-to-maturity securities, fair value		140
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Agency [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	3,002	3,094
Securities available for sale debt securities, unrealized gains	141	42
Securities available for sale debt securities, unrealized losses	(3)	(18)
Investment securities – available for sale	3,140	3,118
Held to maturity securities, amortized cost		59
Held-to-maturity securities, unrealized gains		1
Held-to-maturity securities, fair value		60
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Non-agency [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	4,134	3,352
Securities available for sale debt securities, unrealized gains	57	29
Securities available for sale debt securities, unrealized losses	(152)	(9)
Investment securities – available for sale	4,039	3,372
Held to maturity securities, amortized cost		430
Held-to-maturity securities, unrealized gains		4
Held-to-maturity securities, fair value		434
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	5,312	5,044
Securities available for sale debt securities, unrealized gains	96	78
Securities available for sale debt securities, unrealized losses	(40)	(8)
Investment securities – available for sale	5,368	5,114
Held to maturity securities, amortized cost		52
Held-to-maturity securities, fair value		52
Other [Member]
Debt Securities, Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	4,856	2,788
Securities available for sale debt securities, unrealized gains	301	121
Securities available for sale debt securities, unrealized losses	(2)	(1)
Investment securities – available for sale	5,155	2,908
Held to maturity securities, amortized cost	656	1,792
Held-to-maturity securities, unrealized gains	42	85
Held-to-maturity securities, unrealized losses	(14)	(14)
Held-to-maturity securities, fair value	$ 684	$ 1,863