Investment Securities (Summary) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	$ 63,514		$ 56,625
Securities available for sale debt securities, unrealized gains	710		854
Securities available for sale debt securities, unrealized losses	(835)		(446)
Securities available for sale debt securities, fair value	63,389		57,033
Securities available for sale, amortized cost	63,514		57,212
Securities available for sale, unrealized gains	710		854
Securities available for sale, unrealized losses	(835)		(448)
Securities available for sale, fair value	63,389		57,618
Debt Securities, Held-to-maturity	19,312		18,513
Held-to-maturity securities, unrealized gains	118		224
Held-to-maturity securities, unrealized losses	(411)		(172)
Held-to-maturity securities, fair value	19,019		18,565
US Treasury and Government Agencies Securities
Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	18,104		14,432
Securities available for sale debt securities, unrealized gains	133		173
Securities available for sale debt securities, unrealized losses	(137)		(84)
Securities available for sale debt securities, fair value	18,100		14,521
Debt Securities, Held-to-maturity	758		741
Held-to-maturity securities, unrealized gains	28		37
Held-to-maturity securities, unrealized losses	(23)		(13)
Held-to-maturity securities, fair value	763		765
Residential mortgage-backed Securities | Mortgage-backed Securities Agency
Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	29,413		25,534
Securities available for sale debt securities, unrealized gains	104		121
Securities available for sale debt securities, unrealized losses	(524)		(249)
Securities available for sale debt securities, fair value	28,993		25,406
Debt Securities, Held-to-maturity	15,740		14,503
Held-to-maturity securities, unrealized gains	32		77
Held-to-maturity securities, unrealized losses	(358)		(139)
Held-to-maturity securities, fair value	15,414		14,441
Residential mortgage-backed Securities | Mortgage-backed Securities Non-agency
Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	1,924		2,443
Securities available for sale debt securities, unrealized gains	300		336
Securities available for sale debt securities, unrealized losses	(13)		(21)
Securities available for sale debt securities, fair value	2,211		2,758
Debt Securities, Held-to-maturity	152		167
Held-to-maturity securities, unrealized gains	2		7
Held-to-maturity securities, fair value	154		174
Commercial Mortgage Backed Securities | Mortgage-backed Securities Agency
Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	2,630		1,960
Securities available for sale debt securities, unrealized gains	13		2
Securities available for sale debt securities, unrealized losses	(66)		(58)
Securities available for sale debt securities, fair value	2,577		1,904
Debt Securities, Held-to-maturity	143		407
Held-to-maturity securities, unrealized gains	1		4
Held-to-maturity securities, unrealized losses	(1)
Held-to-maturity securities, fair value	143		411
Commercial Mortgage Backed Securities | Mortgage-backed Securities Non-agency
Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	2,689		2,603
Securities available for sale debt securities, unrealized gains	5		19
Securities available for sale debt securities, unrealized losses	(37)		(9)
Securities available for sale debt securities, fair value	2,657		2,613
Debt Securities, Held-to-maturity	488		538
Held-to-maturity securities, unrealized gains	1		10
Held-to-maturity securities, unrealized losses	(1)
Held-to-maturity securities, fair value	488		548
Asset-backed Securities
Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	4,933		5,331
Securities available for sale debt securities, unrealized gains	59		74
Securities available for sale debt securities, unrealized losses	(20)		(8)
Securities available for sale debt securities, fair value	4,972		5,397
Debt Securities, Held-to-maturity	182		200
Held-to-maturity securities, unrealized gains	1		1
Held-to-maturity securities, fair value	183		201
Other debt
Available-for-sale [Line Items]
Securities available for sale debt securities, amortized cost	3,821		4,322
Securities available for sale debt securities, unrealized gains	96		129
Securities available for sale debt securities, unrealized losses	(38)		(17)
Securities available for sale debt securities, fair value	3,879		4,434
Debt Securities, Held-to-maturity	1,849		1,957
Held-to-maturity securities, unrealized gains	53		88
Held-to-maturity securities, unrealized losses	(28)		(20)
Held-to-maturity securities, fair value	$ 1,874		2,025
Corporate Stocks And Other
Available-for-sale [Line Items]
Securities available for sale equity securities, amortized cost			587
Securities available for sale equity securities, unrealized losses			(2)
Securities available for sale equity securities, fair value			$ 585
Accounting Standards Update 2016-01
Available-for-sale [Line Items]
Securities reclassified to equity investments		$ 600