Variable Interest Entities Variable Interest Entities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Non Interest Expenses [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Measure of Activity, Income or Loss before Tax	$ 15	$ 11
Income Tax Expense [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Measure of Activity, Amortization of Investments	118	116
Variable Interest Entity, Measure of Activity, Tax Credits and Other Benefits	$ 175	$ 164