v3.8.0.1
Income Taxes - Narrative (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Operating Loss Carryforwards [Line Items]    
Decrease in valuation allowance $ 5  
Impact of a multi-year reserve for deductions related to domestic production activities 143  
Unrecognized tax benefits that would impact effective tax rate 225  
Decrease in unrecognized tax benefits is reasonably possible 8  
Net interest expense and penalties related to uncertain tax positionse 4  
Accrued interest and penalties for uncertain tax position 9 $ 5
Tax Cuts And Jobs Act Of 2017, incomplete accounting, provisional income tax benefit $ 125  
Projected effective rate at which position will reverse for deferred tax assets and liabilities 21.00%  
Tax Cuts And Jobs Act Of 2017, incomplete accounting, change in tax rate, deferred tax asset, provisional income tax expense $ 126  
Tax Cuts And Jobs Act Of 2017, incomplete accounting, transition tax for accumulated foreign earnings, provisional income tax expense 1  
Domestic Tax Authority    
Operating Loss Carryforwards [Line Items]    
Operating loss and tax credit carryforwards 44  
State and Local Jurisdiction    
Operating Loss Carryforwards [Line Items]    
Operating loss and tax credit carryforwards $ 42