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Basis of Presentation and Significant Accounting Policies - Summary of Deferred Revenue (Detail) - USD ($)
$ in Thousands
Sep. 30, 2019
Dec. 31, 2018
Deferred Revenue Arrangement [Line Items]    
Contract liabilities $ 5,414 $ 5,496
Short-term Contract with Customer [Member]    
Deferred Revenue Arrangement [Line Items]    
Contract liabilities 5,016 5,165
Long-term Contract with Customer [Member]    
Deferred Revenue Arrangement [Line Items]    
Contract liabilities $ 398 $ 331