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Revenue - Summary of Changes in Certain Contract Assets and Liabilities (Detail) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Disaggregation of Revenue [Line Items]    
Accounts receivable $ 38,537 $ 43,673
Deferred revenue (5,232) (3,820)
Deferred expenses 1,216 501
Customer prepayments (1,349) (1,250)
Sales allowances (640) $ (548)
Accounting Standards Update 2014-09 [Member]    
Disaggregation of Revenue [Line Items]    
Accounts receivable (5,136)  
Deferred revenue (1,412)  
Deferred expenses 715  
Customer prepayments (99)  
Sales allowances $ (92)