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Revenue Recognition - Additional Information (Detail) - USD ($)
$ in Thousands
9 Months Ended
Sep. 30, 2019
Dec. 31, 2018
Revenue Recognition [Abstract]    
Period of revenue from services 1 month  
Subscription revenue term, minimum 1 year  
Subscription revenue term, maximum 3 years  
Aggregate amount of transaction price from contractual obligations $ 15,770 $ 17,496