Background and Basis of Presentation (Share Repurchase Table) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Repurchase of common stock (shares)	2.6	1.2	8.1	10.0
Repurchases of common stock, value	$ 171	$ 63	$ 512	$ 518	$ 554
Average price of repurchased shares, per share (usd per share)	$ 66.23	$ 50.39	$ 63.28	$ 51.47