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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Accounting Policies [Abstract]      
Increase in costs and expenses after reclassification   $ 33,797  
Costs and expenses $ 59,153 $ 56,799  
Deferred revenue 219   $ 265
Deferred evenue recognized into revenue 265    
Unbilled revenue in accounts receivable $ 18,463   $ 16,238