Background and Basis of Presentation (Share Repurchase Table) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Repurchase of common stock, shares	2.7	5.2	5.5	8.8
Repurchases of common stock, value	$ 173	$ 263	$ 341	$ 455	$ 554
Average price of repurchased shares, per share (usd per share)	$ 64.06	$ 50.64	$ 61.90	$ 51.63