Liquidity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended						9 Months Ended
	Jun. 26, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Cash And Cash Equivalents [Line Items]
Net loss		$ (8,545)	$ (7,384)	$ (5,858)	$ 889	$ (10,008)	$ (7,030)	$ (21,787)	$ (16,149)
Accumulated deficit		(179,593)						(179,593)		$ (157,806)
Cash and cash equivalents		$ 56,137						56,137		$ 20,733
Net cash used in operating activities								(18,357)	$ (12,299)
Proceeds from sale of common stock, net of costs								$ 53,760
Underwritten Public Offering [Member]
Cash And Cash Equivalents [Line Items]
Sale of common stock in public offering, net of costs, (shares)	34,848,484
Price per unit	$ 1.65
Proceeds from sale of common stock, net of costs	$ 53,700