Variable Interest Entities - Unconsolidated LIHC Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Non Interest Expenses
Noncontrolling Interest [Line Items]
Losses from LIHC investments included in other noninterest expense	$ 4	$ 2	$ 8	$ 5
Income Tax Expense
Noncontrolling Interest [Line Items]
Amortization of LIHC investments included in income tax expense	37	34	106	96
Tax credits and other tax benefits from LIHC investments included in income tax expense	$ 49	$ 47	$ 141	$ 139