Other Assets (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Jul. 31, 2010	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Company limited partner holding interest, percentage	99.90%
Variable Interest Entity, Assets		$ 295		$ 315
Affordable Housing Tax Credits and Other Tax Benefits, Amount		23	$ 18
Unamortized investment balance classified as Other Assets		231		265
Maximum exposure to loss		$ 231		$ 265
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
General partner holding interest, percentage	0.10%