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Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Income Tax Disclosure [Abstract]      
Effective tax rate (13.70%) (5.90%)  
Federal statutory rate 21.00%   35.00%
Decrease in income tax due to change in fair value of contingent consideration $ 1.2 $ (3.0)