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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]          
Provision (benefit) for income taxes, as a percentage of income before income taxes 0.00% 22.40% 38.20% 34.60%  
Statutory U.S. federal income tax rate 35.00% 35.00% 35.00% 35.00%  
Liability related to unrecognized tax benefits $ 4.9   $ 4.9   $ 6.8