Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts and estimated returns
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance of valuation allowance and reserves	$ 73	$ 59	$ 54
Charged to Costs and Expenses, additions	8	18	7
Other, additions	0	0	0
Deductions	4	4	2
Ending balance of valuation allowance and reserves	77	73	59
Valuation allowance for deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance of valuation allowance and reserves	0	0	0
Charged to Costs and Expenses, additions	9	0	0
Other, additions	0	0	0
Deductions	0	0	0
Ending balance of valuation allowance and reserves	$ 9	$ 0	$ 0