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Changes in Deferred Revenue (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Jan. 01, 2018
Dec. 31, 2017
Disaggregation Of Revenue [Line Items]      
Deferred revenue $ 2,810   $ 1,090
Fair value of deferred revenue acquired in acquisition, net of recognition 1,582    
Deferral of revenue billed in current period, net of recognition 1,098    
Recognition of revenue deferred in prior periods $ (958)    
Topic 606      
Disaggregation Of Revenue [Line Items]      
Deferred revenue   $ 1,088  
Topic 606 | Impact of Adoption of Topic 606      
Disaggregation Of Revenue [Line Items]      
Deferred revenue   $ (2)