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Stock-Based Compensation - Additional Information (Detail) - $ / shares
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Stock issuances under equity compensation plans 2,854,816 1,518,605
Stock Options [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted stock options 209,700 328,860
Weighted average grant-date fair value $ 68.88 $ 7.94
Restricted Stock Units (RSU) [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Awards granted 10,000 0