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
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at End of Period		$ 4
Allowance for Bad Debts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	65	72	65
Charged to Expense / Reduction in Revenue	10	(1)	39
Deductions	(1)	(6)	(32)
Balance at End of Period	74	65	72
Allowance for Sales Returns
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	76	86	133
Charged to Expense / Reduction in Revenue	89	55	17
Deductions	(95)	(65)	(64)
Balance at End of Period	70	76	86
Tax Valuation Allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	211	183	151
Charged to Expense / Reduction in Revenue	1	32	33
Deductions	(86)	(4)	(1)
Balance at End of Period	$ 126	$ 211	$ 183