Stock-Based Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	6 Months Ended	9 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2020 USD ($) $ / shares shares
Number of Shares
Beginning balance (in shares) | shares	1,297,029	1,297,029
Granted (in shares) | shares		498,662
Exercised (in shares) | shares		(17,689)
Forfeited (in shares) | shares		(164,978)
Ending balance (in shares) | shares		1,613,024
Number of shares Options, Exercisable (in shares) | shares		682,632
Number of shares Options, Vested and expected to vest (in shares) | shares		1,404,246
Weighted Average Exercise Price
Beginning balance (in usd per share) | $ / shares	$ 17.05	$ 17.05
Granted (in usd per share) | $ / shares		9.13
Exercised (in usd per share) | $ / shares		7.25
Forfeited (in usd per share) | $ / shares		21.68
Ending balance (in usd per share) | $ / shares		14.24
Weighted average exercise price, Exercisable (in usd per share) | $ / shares		18.23
Weighted average exercise price, Vested and expected to vest (in usd per share) | $ / shares		$ 14.43
Weighted average contractual term outstanding (in years)	8 years 4 months 24 days	8 years 2 months 12 days
Weighted average contractual term outstanding, Exercisable (in years)		7 years
Weighted average contractual term outstanding, Vested and expected to vest (in years)		8 years 1 month 6 days
Aggregate intrinsic value, Beginning balance | $	$ 1,286	$ 1,286
Aggregate intrinsic value, Ending balance | $		0
Aggregate intrinsic value, exercisable | $		0
Aggregate intrinsic value, vested and expected to vest | $		$ 0