Other Financial Information (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid expenses	$ 57	$ 45
Other	72	80
Total other current assets	129	125
Other Liabilities, Current [Abstract]
Accounts payable	491	464
Capital expenditures incurred but not paid	$ 38	$ 44