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Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 79 Months Ended
May 31, 2018
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2017
Jun. 06, 2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Common stock reserved for future issuance   11,505,529      
Unrecognized compensation expense   $ 0.1      
Unrecognized stock-based compensation expense, weighted average period of recognition   5 months 8 days      
Restricted Stock Units (RSUs)          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Unrecognized compensation expense   $ 4.8      
Unrecognized stock-based compensation expense, weighted average period of recognition   2 years 10 months 24 days      
Repurchase of common stock (in shares)   42,880 42,447    
2007 Plan and 2010 Plan          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Common stock reserved for future issuance   0      
Number of shares available for grants         459,956
2011 Plan          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Common stock reserved for future issuance         400,000
Number of shares available for grants         859,956
Increase in shares of common stock authorized for issuance 500,000     3,000,000