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Commitments and Contingencies - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Commitments And Contingencies Disclosure [Line Items]    
Capital lease assets $ 58.7 $ 63.4
Assets fully depreciated 32.0 26.8
Capital leased assets, net book value 9.5 $ 13.0
Purchase obligation, 2019 16.4  
Purchase obligation, 2020 21.4  
Purchase obligation, 2021 15.0  
Chemical Supplier [Member]    
Commitments And Contingencies Disclosure [Line Items]    
Purchase obligation, 2019 $ 0.6  
Minimum [Member]    
Commitments And Contingencies Disclosure [Line Items]    
Estimated life of capital lease 4 years  
Noncancellable operating leases, renewal period 1 year  
Maximum [Member]    
Commitments And Contingencies Disclosure [Line Items]    
Estimated life of capital lease 6 years  
Noncancellable operating leases, renewal period 5 years