Certain Transfers of Financial Assets and Variable Interest Entities Community Development Tax Credits and Amortization (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Affordable Housing Tax Credits and Other Tax Benefits, Amount		$ 28	$ 27	$ 87	$ 77
Amortization Method Qualified Affordable Housing Project Investments, Amortization		29	27	92	76
Investment Tax Credit			25
Amortization of Intangible Assets	[1]			13	16
Variable Interest Entity, Not Primary Beneficiary [Member]
Investment Tax Credit				62	60
Amortization of Intangible Assets		19	$ 19	$ 49	$ 45
Community Development Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Investment Tax Credit		$ 23

[1] Does not include expense associated with community development investments. See Note 10, "Certain Transfers of Financial Assets and Variable Interest Entities," for additional information.