Annual report pursuant to Section 13 and 15(d)

Stock and Employee Benefit Plans - Additional Information (Details)

v3.8.0.1
Stock and Employee Benefit Plans - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended 18 Months Ended
Jun. 28, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]        
Stock-based compensation expense   $ 3,046 $ 1,905  
Unrecognized compensation costs related to nonvested awards   $ 6,400   $ 6,400
Weighted-average compensation cost recognition period   3 years 3 months 11 days    
Matching contributions made to employee benefit plans   $ 45 32  
Research and development        
Defined Benefit Plan Disclosure [Line Items]        
Stock-based compensation expense   844 599  
General and administrative        
Defined Benefit Plan Disclosure [Line Items]        
Stock-based compensation expense   $ 2,202 $ 1,306  
2014 Stock Plan        
Defined Benefit Plan Disclosure [Line Items]        
Number of options granted (in shares)       0
Shares available for future grant (in shares) 0      
Shares forfeited (in shares)   194,542    
2016 Stock Plan        
Defined Benefit Plan Disclosure [Line Items]        
Number of options granted (in shares)   1,852,682 1,873,047  
Shares available for future grant (in shares)   1,612,514   1,612,514
Shares of common stock authorized for issuance (in shares) 3,750,000      
Vesting period 4 years      
Maximum term of stock options   10 years    
Weighted-average fair value (in dollars per share)   $ 2.47 $ 1.00  
Executive Officers and Senior Leadership        
Defined Benefit Plan Disclosure [Line Items]        
Number of options granted (in shares)   625,000    
Stock-based compensation expense   $ 800    
Unrecognized compensation costs related to nonvested awards   2,400   $ 2,400
Executive Officers and Senior Leadership | Research and development        
Defined Benefit Plan Disclosure [Line Items]        
Stock-based compensation expense   300 $ 300  
Executive Officers and Senior Leadership | General and administrative        
Defined Benefit Plan Disclosure [Line Items]        
Stock-based compensation expense   $ 500