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Leases - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Operating Leased Assets [Line Items]      
Rent expense for noncancelable operating leases $ 22.4 $ 18.4 $ 15.1
Minimum      
Operating Leased Assets [Line Items]      
Lease renewable period, maximum (in years) 1 year    
Maximum      
Operating Leased Assets [Line Items]      
Lease renewable period, maximum (in years) 5 years