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Commitments and Contingencies - Additional Information (Detail) - USD ($)
$ in Millions
6 Months Ended 12 Months Ended
Jun. 30, 2017
Dec. 31, 2016
Commitments And Contingencies Disclosure [Line Items]    
Capital lease assets $ 64.4 $ 64.2
Assets fully depreciated 23.5 22.8
Capital leased assets, net book value $ 14.8 $ 16.4
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