Other Assets (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Jul. 31, 2010	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Company limited partner holding interest, percentage	99.90%
Tax credits, reduction to income tax expense		$ 31	$ 27
Unamortized investment balance classified as Other Assets		213		$ 265
Maximum exposure to loss		$ 213		$ 265
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
General partner holding interest, percentage	0.10%