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Stock-Based Compensation - Employee Stock Purchase Plan ("ESPP") - Additional Information (Detail) - USD ($)
shares in Thousands, $ in Millions
1 Months Ended 3 Months Ended
Feb. 28, 2019
Aug. 31, 2018
Feb. 28, 2018
Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Offering period       6 months
Employee Stock Purchase Plan ("ESPP") [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage of fair market value to determine purchase price       85.00%
Proceeds of from issuance of shares under ESPP $ 0.3 $ 0.3 $ 0.4  
Options issued 95,376 88,583 68,212  
Rate of discount on fair market value of common stock under ESPP       15.00%
Period of expected life, options granted       5 years