Indebtedness - Textual Information (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jul. 13, 2016	Dec. 31, 2015
Debt Instrument
Total debt, fair value	$ 3,404			$ 3,404			$ 4,321
Total debt	3,022			3,022			$ 4,041
Debt Instrument, Repurchased Face Amount		$ 1,000
Debt Instrument, Purchase Premium		135
Loss on early extinguishment of debt	0	$ (142)	$ 0	(142)	$ 0
Line of Credit Facility
Line of Credit Facility, Maximum Borrowing Capacity	2,500			2,500		$ 2,500
Combined Maximum Maturity of Commercial Paper and Line of Credit	2,500			$ 2,500
Maximum maturity of commercial paper issued				270 days
Commercial Paper, Amount Outstanding	0			$ 0
Line of Credit Facility, Amount Outstanding	$ 0			$ 0