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Contract Balances - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Contract With Customer Asset And Liability [Line Items]          
Write-offs and sales allowances $ 100,000 $ 100,000 $ 892,000 $ 1,053,000  
Revenue, Remaining performance obligation 164,700,000   164,700,000    
Prepaid Expenses and Other Current Assets          
Contract With Customer Asset And Liability [Line Items]          
Assets impairment charges 0 0 0 0  
Contract assets 1,100,000   1,100,000   $ 800,000
Current Deferred Revenue and Advanced Payments          
Contract With Customer Asset And Liability [Line Items]          
Revenue recognized from beginning deferred revenue $ 36,100,000 $ 39,200,000 $ 154,100,000 $ 170,600,000