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Income Taxes (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Income Tax Disclosure [Abstract]        
Effective tax rate (percent) 23.50% 24.80% 23.90% 32.70%
Charge from valuation allowance for tax carryovers     $ 4 $ 3
Tax benefit from resolution of settlement $ 6   $ 20  
Benefit from resolution of tax examinations   $ 15   15
Charge from establishment of valuation allowance   $ 5   $ 5
Percent decrease in unrecognized benefits, reasonably possible (up to) 15.00%   15.00%