Certain Transfers of Financial Assets and Variable Interest Entities Community Development Tax Credits and Amortization (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Affordable Housing Tax Credits and Other Tax Benefits, Amount		$ 29	$ 25	$ 59	$ 50
Amortization Method Qualified Affordable Housing Project Investments, Amortization		31	25	63	49
Investment Tax Credit			19
Amortization of Intangible Assets	[1]			11	10
Variable Interest Entity, Not Primary Beneficiary [Member]
Investment Tax Credit				38	35
Amortization of Intangible Assets		16	$ 14	$ 31	$ 27
Community Development Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Investment Tax Credit		$ 20

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