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Fixed Assets, Net - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Property, Plant and Equipment [Line Items]        
Depreciation expense $ 4.4 $ 3.2 $ 9.3 $ 6.4
Software development costs capitalized 1.6 0.5 2.2 1.0
Operating, Administrative and Other [Member]        
Property, Plant and Equipment [Line Items]        
Amortization of software development costs $ 0.6 $ 0.2 $ 1.1 $ 0.4