Supplemental Disclosures of Cash Flow (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Cash Flow Information [Abstract]
Interest paid	$ 265	$ 272	$ 260
Income taxes paid (received)	215	254	10
Significant non-cash investing and financing transactions:
Value of stock received from stock options exercised through stock swap transactions		13	$ 5
Other assets received in our financing transaction	$ 252
Other investments received in our repurchase program		$ 152