Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Bad Debts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 74	$ 65	$ 72
Charged to Expense / Reduction in Revenue	33	10	(1)
Deductions	(15)	(1)	(6)
Balance at End of Period	92	74	65
Allowance for Sales Returns
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	70	76	86
Charged to Expense / Reduction in Revenue	128	89	55
Deductions	(104)	(95)	(65)
Balance at End of Period	94	70	76
Tax Valuation Allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	126	211	183
Charged to Expense / Reduction in Revenue	43	1	32
Deductions	(25)	(86)	(4)
Balance at End of Period	$ 144	$ 126	$ 211