Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts and estimated returns
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance of valuation allowance and reserves	$ 77	$ 73	$ 59
Charged to Costs and Expenses, additions	15	8	18
Other, additions	0	0	0
Deductions	10	4	4
Ending balance of valuation allowance and reserves	82	77	73
Valuation allowance for deferred tax assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance of valuation allowance and reserves	9	0	0
Charged to Costs and Expenses, additions	45	9	0
Other, additions	0	0	0
Deductions	0	0	0
Ending balance of valuation allowance and reserves	$ 54	$ 9	$ 0