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Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended
Jul. 15, 2015
Jul. 14, 2015
Mar. 31, 2017
Mar. 31, 2016
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of common stock shares reserved for issuance     9,801,151   8,636,175
Accounting Standards Update 2016-09 [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Cumulative effect of adoption of new accounting standard     $ 8    
2015 Employee Stock Purchase Plan [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of common stock shares reserved for issuance 700,000   700,000   700,000
Stock option grants description     The number of shares initially reserved for issuance under the ESPP will increase automatically on January 1 for nine years from the first offering date by the number of shares equal to 1% of the total outstanding shares of the Company's common stock as of the immediately preceding December 31.    
Percentage threshold of outstanding shares increased annually under the plan 1.00%        
Maximum number of common stock shares allowed to issue under employee stock purchase plan 3,400,000        
Options to purchase shares of common stock, discount percentage 15.00%        
Number of common stock issued     0    
2015 Plan [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of common stock shares reserved for issuance     6,420,411    
Stock option grants description     The number of shares reserved for issuance under the 2015 Plan will increase automatically on January 1 of each calendar year 2016 through 2025 by the number of shares equal to 4% of the total outstanding shares of the Company's common stock as of the immediately preceding December 31.    
Percentage threshold of outstanding shares increased annually under the plan   4.00%      
Stock option life in years     10 years    
2008 Plan and 2015 Plan [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of common stock shares reserved for issuance     1,486,099   1,392,521
Weighted-average grant date fair values of options granted     $ 1.12 $ 5.00  
Aggregate intrinsic value of options exercised     $ 100 $ 800  
Total grant date fair value of options vested     2,200 $ 700  
Total unrecognized stock-based compensation related to unvested stock options     $ 14,000    
Weighted-average period     2 years 6 months