Common Stock and Stock-Based Awards - Common Stock - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended
	Aug. 12, 2020 USD ($) $ / shares shares	Nov. 27, 2019 USD ($)	Sep. 30, 2020 $ / shares shares	Jun. 30, 2019 shares	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net proceeds from sale of common stock | $					$ 244,020	$ 60,527
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares issued			12,075,000	28,818,578
Cowen and Company, LLC and Piper Sandler & Co. [Member] | Underwriting Agreement [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares issued	10,500,000
Common stock, share price | $ / shares	$ 21.50
Option exercisable period for purchase additional shares	30 days
Cowen and Company, LLC and Piper Sandler & Co. [Member] | Underwriting Agreement [Member] | Common Stock [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option to purchase additional shares of common stock	1,575,000
Nestlé [Member] | Securities Purchase Agreement [Member] | Concurrent Placement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares issued	959,002
Common stock, share price | $ / shares	$ 20.855
Net proceeds from sale of common stock | $	$ 19,900
Cowen And Company, LLC [Member] | 2019 Sales Agreement [Member] | At The Market Equity Offering Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Gross proceeds from sale of common stock | $		$ 25,000
Cowen And Company, LLC [Member] | 2019 and 2020 Sales Agreement [Member] | At The Market Equity Offering Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares issued					5,787,681
Common stock, share price | $ / shares			$ 4.40		$ 4.40
Net proceeds from sale of common stock | $					$ 24,772
Percentage of commission on sale of common stock			3		3