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Income Taxes - Summary of Information Related to Interest and Penalties on Uncertain Tax Positions (Detail) - USD ($)
$ in Millions
9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Income Tax Disclosure [Abstract]      
Interest expense (income) $ 0.3 $ 0.2  
Accrued interest payable $ 0.8   $ 0.5