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Summary of Significant Accounting Policies - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2016
USD ($)
Customer
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Summary Of Significant Accounting Policy [Line Items]      
Original maturities 90 days    
Number of customers accounted for revenues or accounts receivable greater than 2% of total | Customer 0    
Annual goodwill impairment test, period November 30th    
Goodwill impairment charges $ 0 $ 0 $ 0
Non-current deferred rent liabilities 7,400,000 6,400,000  
Foreign exchange gains (losses) $ 100,000   $ (100,000)
Percentage of expense over the service period on share based awards 100.00%    
Unamortized fair value stock based compensation $ 15,500,000    
Weighted average remaining recognition period 2 years 6 months    
ASU No. 2016-09 [Member]      
Summary Of Significant Accounting Policy [Line Items]      
Change in reclassification of tax withholding $ 2,100,000 $ 1,500,000  
Research Service Revenue [Member] | Customer Concentration Risk [Member]      
Summary Of Significant Accounting Policy [Line Items]      
Customer accounted for percentage 2.00%    
Accounts Receivable [Member] | Credit Concentration Risk [Member]      
Summary Of Significant Accounting Policy [Line Items]      
Customer accounted for percentage 2.00%