Stockholders' Equity - 2019 Equity Financing - Additional Information (Detail) - USD ($)		1 Months Ended		3 Months Ended		9 Months Ended
	Apr. 01, 2019	Aug. 31, 2020	Jan. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
At-the-Market Offering [Member]
Class of Stock [Line Items]
Common stock shares maximum aggregate offering price		$ 25,000,000.0	$ 20,000,000.0
Stock issuances, sales agent commission maximum percentage		3.00%	3.00%
Common stock issued				6,029,465	1,707,995	6,029,465	1,707,995
Weighted average common stock price per share				$ 0.81	$ 1.50	$ 0.81	$ 1.50
Gross proceeds from issuance of common stock				$ 4,900,000	$ 2,600,000	$ 4,900,000	$ 2,600,000
Share issuance costs				$ 250,000	$ 151,000	$ 250,000	$ 151,000
2019 Equity Financing [Member] | Share Offering [Member]
Class of Stock [Line Items]
Common stock issued	10,526,500
Gross proceeds from issuance of common stock	$ 20,000,000.0
Share issuance costs	$ 1,700,000
Price per share	$ 1.90