Schedule II - Valuation and Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts and estimated returns
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation Allowances and Reserves, Beginning Balance	$ 67	$ 61	$ 49
Valuation Allowances and Reserves, Charged to Cost and Expense	0	15	18
Valuation Allowances and Reserves, Charged to Other Accounts	0	0	0
Valuation Allowances and Reserves, Deductions	13	9	6
Valuation Allowances and Reserves, Ending Balance	54	67	61
Valuation allowance for deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation Allowances and Reserves, Beginning Balance	6	1	1
Valuation Allowances and Reserves, Charged to Cost and Expense	0	6	0
Valuation Allowances and Reserves, Charged to Other Accounts	0	0	0
Valuation Allowances and Reserves, Deductions	6	1	0
Valuation Allowances and Reserves, Ending Balance	$ 0	$ 6	$ 1