Stockholders' Equity Common Stock - Additional Information (Detail) $ / shares in Units, $ in Thousands					12 Months Ended
	Aug. 12, 2020 USD ($) $ / shares shares	Nov. 27, 2019 USD ($) $ / shares	Jun. 21, 2019 USD ($) $ / shares shares	Jun. 18, 2019 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2021 $ / shares shares	Jul. 01, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized					200,000,000		200,000,000
Common stock, par value | $ / shares					$ 0.001		$ 0.001
Net proceeds from sale of common stock | $					$ 243,748	$ 60,527
Underwriting Agreement [Member] | Cowen and Company, LLC and Piper Sandler & Co. [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net proceeds from sale of common stock | $	$ 243,748
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares issued					12,075,000	28,818,578
Common Stock [Member] | Underwriting Agreement [Member] | Cowen and Company, LLC and Piper Sandler & Co. [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
Common Stock [Member] | Maximum [Member] | Underwriting Agreement [Member] | Cowen and Company, LLC and Piper Sandler & Co. [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option to purchase additional shares of common stock	1,575,000
Initial Public Offering ("IPO") [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized								200,000,000
Common stock, par value | $ / shares								$ 0.001
Underwritten Public Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net proceeds from sale of common stock | $			$ 4,551	$ 55,976
Underwritten Public Offering [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares issued			2,151,911	26,666,667
Common stock, share price | $ / shares			$ 2.25	$ 2.25
Underwritten Public Offering [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				2,666,666
At The Market Equity Offering Program [Member] | 2019 Sales Agreement [Member] | Cowen And Company, LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value | $ / shares		$ 0.001
Gross proceeds from sale of common stock | $		$ 25,000
At The Market Equity Offering Program [Member] | 2019 and 2020 Sales Agreement [Member] | Cowen And Company, LLC [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
Net proceeds from sale of common stock | $					$ 24,773
Percentage of commission on sale of common stock					3
Concurrent Placement [Member] | Securities Purchase Agreement [Member] | Nestlé [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