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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
Dec. 31, 2016
Income Tax Disclosure [Abstract]          
Effective income tax rate (as percent) 36.50% 35.30% 35.90% 37.30%  
U.S. Federal statutory rate (as percent) 35.00%        
Gross unrecognized tax benefits, including interest and penalties $ 39.5   $ 39.5   $ 44.0
Minimum          
Income Tax [Line Items]          
Expected annual effective income tax rate (as percent)     36.00%    
Maximum          
Income Tax [Line Items]          
Expected annual effective income tax rate (as percent)     37.00%