Other Financial Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid expenses	$ 62	$ 46
Other	84	77
Total other current assets	146	123
Accounts Payable, Current [Abstract]
Accounts payable	445	369
Capital expenditures incurred but not paid	$ 26	$ 29