Annual report pursuant to Section 13 and 15(d)

Equity Incentive Plans and Stock Based Compensation - Summary of Stock Option Activity Under Equity Incentive Plan (Detail)

v3.20.1
Equity Incentive Plans and Stock Based Compensation - Summary of Stock Option Activity Under Equity Incentive Plan (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Outstanding Options Number of Shares, Beginning Balance 4,002,999 2,768,711  
Number of Shares, Options granted 2,003,600 1,844,787  
Number of Shares, Options exercised (286,479) (407,682)  
Number of shares, Options canceled (976,130) (202,817)  
Outstanding Options Number of Shares, Ending Balance 4,743,990 4,002,999 2,768,711
Outstanding Options Number of Shares, Vested and expected to vest 4,743,990    
Outstanding Options Number of Shares, Exercisable 1,779,916    
Weighted Average Exercise Price, Beginning Balance $ 10.43 $ 12.07  
Weighted Average Exercise Price, Options granted 6.01 6.98  
Weighted Average Exercise Price, Options exercised 6.10 0.70  
Weighted Average Exercise Price, Options canceled 22.37 20.83  
Weighted Average Exercise Price, Ending Balance 6.37 $ 10.43 $ 12.07
Weighted Average Exercise Price, Vested and expected to vest 6.37    
Weighted Average Exercise Price, Exercisable $ 5.98    
Weighted-Average Remaining Contractual Term, Outstanding 8 years 2 months 12 days 6 years 4 months 24 days 5 years 7 months 6 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest 8 years 2 months 12 days    
Weighted-Average Remaining Contractual Term, Exercisable 7 years    
Aggregate Intrinsic Value, Outstanding $ 36.5 $ 1.5 $ 11.0
Aggregate Intrinsic Value, Vested and expected to vest 36.5    
Aggregate Intrinsic Value, Exercisable $ 14.6