v3.3.1.900
Schedule II - Valuation and Qualifying Accounts (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Allowance for doubtful accounts      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Valuation Allowances and Reserves, Balance $ 21 $ 60 $ 61
Valuation Allowances and Reserves, Charged to Cost and Expense 11 10 7
Valuation Allowances and Reserves, Deductions (7) (5) (9)
Valuation Allowances and Reserves, Other Activity 1 (44) [1] 1
Valuation Allowances and Reserves, Balance 26 21 60
Tax valuation allowance      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Valuation Allowances and Reserves, Balance 747 642 502
Valuation Allowances and Reserves, Charged to Cost and Expense [2] 192 187 125
Valuation Allowances and Reserves, Deductions 0 (15) (17)
Valuation Allowances and Reserves, Other Activity (29) (67) 32
Valuation Allowances and Reserves, Balance $ 910 $ 747 $ 642
[1] Other Activity primarily represents the reclassification of balances related to billing adjustments to accounts receivable.
[2] Additions Charged to Costs and Expenses are primarily related to taxable losses for which the tax benefit has been reserved.