Sales of Equity Securities - Additional Information (Detail) - USD ($)					1 Months Ended			3 Months Ended	6 Months Ended
	May 12, 2021	Apr. 16, 2020	Mar. 04, 2020	Mar. 02, 2020	Jan. 31, 2020	Mar. 31, 2019	Feb. 28, 2019	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Jan. 31, 2018
Class Of Stock [Line Items]
Proceeds from exercise of common stock warrants									$ 18,552	$ 2,379,316
Stock price		$ 4.60	$ 4.10	$ 4.00				$ 4.67	$ 4.67
Fair value of warrants issued					$ 1,900,000
Warrant inducement expense						$ 130,000	$ 60,000			$ 2,102,109
Shares issued in offering		2,230,000	1,600,000	2,300,000				908,044
Net cash proceeds from sale of securities		$ 9,600,000	$ 6,100,000	$ 8,600,000				$ 3,900,000
Sales Agreement [Member] | Sales Agent [Member]
Class Of Stock [Line Items]
Stock price								$ 4.67	$ 4.67
Shares issued in offering								908,044
Net cash proceeds from sale of securities								$ 3,900,000
Number of days prior notice to terminate sales agreement	10 days
Percentage of fixed commission to sales agent rate equal to gross sales price per share of common stock sold under sales agreement	3.00%
Maximum [Member] | Sales Agreement [Member] | Sales Agent [Member]
Class Of Stock [Line Items]
Shares issued in offering	25,000,000
Warrant [Member]
Class Of Stock [Line Items]
Issuance of warrants to purchase shares of common stock											89,657
Stock price					$ 3.495						$ 4.05
Over-allotment Option [Member] | Warrant [Member]
Class Of Stock [Line Items]
Proceeds from exercise of common stock warrants					$ 700,000
Shares issued in offering					192,750
February 2019 March 2019 Warrant Repricing and Exchange Transaction [Member]
Class Of Stock [Line Items]
Proceeds from exercise of common stock warrants					$ 2,300,000
Warrant inducement expense					$ 191,000
February 2019 March 2019 Warrant Repricing and Exchange Transaction [Member] | Warrant [Member]
Class Of Stock [Line Items]
Issuance of warrants to purchase shares of common stock					692,725						692,725