Stock Based Compensation - Summary of Stock Option Activity (Detail)	3 Months Ended	9 Months Ended
	Sep. 30, 2019 shares	Sep. 30, 2020 $ / shares shares
Number of shares
Beginning balance (in shares) | shares		5,318,759
Options granted (in shares) | shares		845,120
Less:
Options exercised (in shares) | shares	289,081	1,276,144
Options canceled or expired (in shares) | shares		63,169
Ending balance (in shares) | shares		4,824,566
Exercisable at September 30, 2020 (in shares) | shares		2,552,710
Weighted Average Exercise Price
Weighted average exercise price, beginning balance (in dollars per share) | $ / shares		$ 9.97
Weighted average exercise price, granted (in dollars per share) | $ / shares		28.33
Less:
Weighted average exercise price, exercised (in dollars per share) | $ / shares		7.75
Weighted average exercise price, canceled or expired (in dollars per share) | $ / shares		15.82
Weighted average exercise price, ending balance (in dollars per share) | $ / shares		13.72
Weighted average exercise price, exercisable, ending balance (in dollars per share) | $ / shares		$ 8.86