Other Assets (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2010	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Unconsolidated Partnership, assets		$ 315	$ 355
Impairment losses incurred during the year		0	0	$ 0
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Company limited partner holding interest, percentage	99.90%
Affordable Housing Tax Credits and Other Tax Benefits, Amount		29	35
Unamortized investment balance classified as Other Assets		265	314
Remaining commitments classified as Other Liabilities		0	18
Maximum exposure to loss		$ 265	$ 314
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
General partner holding interest, percentage	0.10%