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Contract Balances - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Contract With Customer Asset And Liability [Line Items]      
Bad debt expense and write-offs (reversals) $ 1,900,000 $ 2,300,000 $ 200,000
Revenue, Remaining performance obligation 183,000,000    
Prepaid Expenses and Other Current Assets      
Contract With Customer Asset And Liability [Line Items]      
Assets impairment charges 0 0 0
Contract assets 800,000 1,200,000  
Current Deferred Revenue and Advanced Payments      
Contract With Customer Asset And Liability [Line Items]      
Revenue recognized from beginning deferred revenue $ 194,600,000 $ 196,700,000 $ 187,300,000