Stockholders' Equity - Common Stock - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended	9 Months Ended		12 Months Ended
	Jan. 31, 2021	Jun. 19, 2020	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Nov. 30, 2017
Sale Of Common Stock [Line Items]
Common stock, shares issued			32,656,480	32,656,480		26,621,954
Proceeds from issuance of common stock, net				$ 13,070,154
Common stock, value of shares issuable							$ 16,000,000.0
Common stock , weighted average price per share			$ 1.47	$ 1.47	$ 2.42
Options Granted [Member]
Sale Of Common Stock [Line Items]
Number of stock options granted		437,500		1,682,000	1,172,000
Public Offering [Member]
Sale Of Common Stock [Line Items]
Common stock, shares issued	5,750,000
Shares issued, price per share	$ 2.50
Proceeds from issuance of common stock, net	$ 14,400,000
Proceeds from issuance of common stock net of underwriting discounts and commissions and offering expenses	$ 13,100,000
FBR Sales Agreement [Member]
Sale Of Common Stock [Line Items]
Common stock, shares issued			0	0	1,395,855
FBR Sales Agreement [Member] | Maximum [Member]
Sale Of Common Stock [Line Items]
Proceeds from issuance of common stock, net					$ 3,300,000
At The Market Offerings [Member]
Sale Of Common Stock [Line Items]
Common stock, shares issued			217,100	217,100
Proceeds from issuance of common stock, net			$ 313,000	$ 313,000
At The Market Offerings [Member] | Maximum [Member]
Sale Of Common Stock [Line Items]
Potential proceeds from issuance of common stock, net						$ 30,000,000