Annual report pursuant to Section 13 and 15(d)

Equity Incentive Plans and Stock Based Compensation - Additional Information (Detail)

v3.19.1
Equity Incentive Plans and Stock Based Compensation - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Aug. 01, 2017
Jan. 01, 2017
May 31, 2018
Aug. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Apr. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Total intrinsic value of stock options exercised         $ 2,600,000 $ 78,000  
Cash received from stock option exercises         283,000 61,000  
Tax benefit realized upon exercise of option         0    
Stock-based compensation expense         3,992,000 1,792,000  
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans         $ 13,000,000    
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans, period for recognition         2 years 10 months 24 days    
2014 Equity Incentive Plan              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Exercise price as a percentage of fair market value of common stock       100.00%      
Terms of stock options granted         10 years    
Terms of stock options vested         4 years    
Options reserved for issuance transferred to 2018 Equity Incentive Plan             322,290
Stock-based compensation expense related to acceleration of vesting of pre-merger awards $ 1,200,000         $ 1,200,000  
2009 Equity Incentive Plan              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Terms of stock options vested         5 years    
Percentage of shares vesting on one-year anniversary and equal monthly vesting installments thereafter         20.00%    
Options reserved for issuance transferred to 2018 Equity Incentive Plan             104,184
2004 Equity Incentive Plan              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Exercise price as a percentage of fair market value of common stock         100.00%    
Terms of stock options granted         10 years    
Terms of stock options vested         4 years    
2018 Equity Incentive Plan              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Exercise price as a percentage of fair market value of common stock     100.00%        
Terms of stock options granted         10 years    
Terms of stock options vested         4 years    
Options to purchase shares of common stock available for future grants         595,710    
Options reserved for issuance transferred to 2018 Equity Incentive Plan             2,000,000
Common stock additional shares may be added to plan in connection in forfeiture or expiration of awards outstanding     2,885,121        
2018 Equity incentive plan annual evergreen provision to increase available for issuance description         Additionally, the number of shares of common stock that may be issued under the 2018 Plan will automatically increase on each January 1, beginning with January 1, 2019, and continuing with January 1, 2028 by an amount equal to the lesser of (i) 4% of the number of outstanding shares of common stock on that date and (ii) an amount determined by the Company’s board of directors or compensation committee; provided, however, that in no event will the number of shares available for issuance under the 2018 Plan be increased to the extent such increase, in addition to any other increases proposed by the board of directors in the number of shares available for issuance under all other employee or director stock plan would result in the total number of shares then available for issuance under all employee and director stock plans exceeding 20% of the outstanding shares of the Company’s common stock on the first day of the applicable fiscal year.    
Annual evergreen provision to increase available for issuance not to exceed percentage of common stock shares outstanding on date of increase     4.00%        
2018 Equity Incentive Plan | Maximum              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Available for issuance for all plans not to exceed percentage of common stock outstanding on first day of fiscal year     20.00%        
2004 Employee Stock Purchase Plan              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Options to purchase shares of common stock available for future grants         18,917    
Additional shares authorized for issuance   9,091          
Offering period         24 months    
Purchase period         6 months    
Discount available to eligible employees related to employee stock purchase plan         85.00%    
Plan participants purchased shares         0 2,868  
Average purchase price under 2004 Employee Stock Purchase Plan           $ 2.80