Variable Interest Entities - Unconsolidated LIHC Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other Non Interest Expenses
Noncontrolling Interest [Line Items]
Losses from LIHC investments included in other noninterest expense	$ 2	$ 2	$ 4	$ 4
Income Tax Expense
Noncontrolling Interest [Line Items]
Amortization of LIHC investments included in income tax expense	34	36	68	69
Tax credits and other tax benefits from LIHC investments included in income tax expense	$ 47	$ 47	$ 91	$ 92