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Revenue Recognition - Summary of Changes in Certain Contract Assets and Liabilities (Detail) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Disaggregation of Revenue [Line Items]    
Accounts receivable $ 41,634 $ 34,487
Deferred revenue (1,419) (5,015)
Deferred expenses 624 377
Customer prepayments (1,350) $ (776)
Sales allowances (384)  
Accounting Standards Update 2014-09 [Member]    
Disaggregation of Revenue [Line Items]    
Accounts receivable 7,147  
Deferred revenue (3,596)  
Deferred expenses 247  
Customer prepayments 574  
Sales allowances $ 384