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Contract Balances - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Contract With Customer Asset And Liability [Line Items]          
Write-offs and sales allowances $ 0 $ 800,000 $ 800,000 $ 900,000  
Revenue, Remaining performance obligation 181,000,000.0   181,000,000.0    
Prepaid Expenses and Other Current Assets          
Contract With Customer Asset And Liability [Line Items]          
Assets impairment charges 0 0 0 0  
Contract assets 800,000   800,000   $ 800,000
Current Deferred Revenue and Advanced Payments          
Contract With Customer Asset And Liability [Line Items]          
Revenue recognized from beginning deferred revenue $ 51,000,000.0 $ 56,800,000 $ 118,000,000.0 $ 131,300,000