Other Financial Information (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid expenses	$ 58	$ 48
Assets held for sale	4	8
Other	63	73
Total other current assets	125	129
Accounts Payable, Current [Abstract]
Accounts payable	366	398
Capital expenditures incurred and included in accounts payable	$ 92	$ 53