Equity Financing - Additional Information (Detail)	1 Months Ended						12 Months Ended
	Jan. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2021 USD ($)	Jan. 28, 2021
Class Of Warrant Or Right [Line Items]
Offering costs allocated to common stock warrant liability and expensed | $							$ 769,000
Registration statement expiration term							This registration statement expired on its three-year anniversary, June 8, 2021.
Maximum [Member]
Class Of Warrant Or Right [Line Items]
Proceeds from issuance, aggregate offering prices | $							$ 50,000,000
March 2018 Purchase Agreement [Member]
Class Of Warrant Or Right [Line Items]
Shares of common stock issued						1,201,634
Warrant issued, shares of common stock called by warrant						1,282,832
Warrants issued, exercise price | $ / shares						$ 10.7258
December 2020 Purchase Agreement [Member]
Class Of Warrant Or Right [Line Items]
Shares of common stock issued		2,618,658
Proceeds from issuance of common stock and warrants gross | $		$ 8,000,000.0
Offering closing period		Dec. 22, 2020
December 2020 Purchase Agreement [Member] | Warrants [Member]
Class Of Warrant Or Right [Line Items]
Warrant issued, shares of common stock called by warrant		2,618,658
Warrants issued, exercise price | $ / shares		$ 3.00
Warrants expiration period		5 years 6 months
September 2019 Purchase Agreement [Member]
Class Of Warrant Or Right [Line Items]
Shares of common stock issued			1,318,828
Proceeds from issuance of common stock and warrants gross | $			$ 10,000,000.0
Offering closing period			Sep. 05, 2019
September 2019 Purchase Agreement [Member] | Warrants [Member]
Class Of Warrant Or Right [Line Items]
Warrant issued, shares of common stock called by warrant			659,414
Warrants issued, exercise price | $ / shares			$ 7.52
Warrants expiration period			5 years 6 months
June 2019 Purchase Agreement [Member]
Class Of Warrant Or Right [Line Items]
Shares of common stock issued				1,489,575
Proceeds from issuance of common stock and warrants gross | $				$ 7,500,000
Offering closing period				Jun. 14, 2019
June 2019 Purchase Agreement [Member] | Warrants [Member]
Class Of Warrant Or Right [Line Items]
Warrant issued, shares of common stock called by warrant				1,489,575
Warrants issued, exercise price | $ / shares				$ 5.00
Warrants expiration period				5 years 6 months
June 2018 Purchase Agreement [Member]
Class Of Warrant Or Right [Line Items]
Shares of common stock issued					1,392,345
Proceeds from issuance of common stock and warrants gross | $					$ 14,000,000.0
Offering closing period					Jun. 14, 2018
June 2018 Purchase Agreement [Member] | Warrants [Member]
Class Of Warrant Or Right [Line Items]
Warrant issued, shares of common stock called by warrant					1,392,345
Warrants issued, exercise price | $ / shares					$ 9.94
Warrants expiration period					5 years 6 months
June 2018 Placement Agent Warrants [Member] | June 2018 Purchase Agreement [Member] | Warrants [Member]
Class Of Warrant Or Right [Line Items]
Warrant issued, shares of common stock called by warrant					69,617
Warrants issued, exercise price | $ / shares					$ 12.568
Warrant, exercisable term					5 years
June 2019 Placement Agent Warrants [Member] | June 2019 Purchase Agreement [Member] | Warrants [Member]
Class Of Warrant Or Right [Line Items]
Warrant issued, shares of common stock called by warrant				74,479
Warrants issued, exercise price | $ / shares				$ 6.2938
Warrant, exercisable term				5 years
September 2019 Placement Agent Warrants [Member] | September 2019 Purchase Agreement [Member] | Warrants [Member]
Class Of Warrant Or Right [Line Items]
Warrant issued, shares of common stock called by warrant			65,942
Warrants issued, exercise price | $ / shares			$ 9.4781
Warrant, exercisable term			5 years
December 2020 Placement Agent Warrants [Member] | December 2020 Purchase Agreement [Member] | Warrants [Member]
Class Of Warrant Or Right [Line Items]
Warrant issued, shares of common stock called by warrant		130,933
Warrants issued, exercise price | $ / shares		$ 3.8188
Warrant, exercisable term		5 years
March 2018 Private Placement [Member] | March 2018 Purchase Agreement [Member]
Class Of Warrant Or Right [Line Items]
Shares of common stock issued						300,752
Warrant issued, shares of common stock called by warrant						300,752
Warrants issued, exercise price | $ / shares						$ 45.75
Warrants expiration period						5 years
Proceeds from issuance of common stock and warrants gross | $						$ 10,000,000.0
March 2018 Private Placement [Member] | March 2018 Placement Agent Warrants [Member] | March 2018 Purchase Agreement [Member]
Class Of Warrant Or Right [Line Items]
Warrant issued, shares of common stock called by warrant						15,038
Warrants issued, exercise price | $ / shares						$ 41.5625
Warrant, exercisable term						5 years
January 2021 Private Placement [Member] | January 2021 Purchase Agreement [Member]
Class Of Warrant Or Right [Line Items]
Shares of common stock issued	7,876,784
Warrant issued, shares of common stock called by warrant	3,938,392
Warrants issued, exercise price | $ / shares	$ 3.13
Warrants expiration period	5 years 6 months
Proceeds from issuance of common stock and warrants gross | $	$ 25,100,000
Remaining offering costs allocated to common stock and offset to additional paid in capital | $	2,000,000.0
January 2021 Private Placement [Member] | January 2021 Purchase Agreement [Member] | Warrants [Member]
Class Of Warrant Or Right [Line Items]
Offering costs allocated to common stock warrant liability and expensed | $	$ 769,000
January 2021 Private Placement [Member] | January 2021 Purchase Agreement [Member] | Warrants [Member] | Expected Volatility [Member]
Class Of Warrant Or Right [Line Items]
Warrants and rights outstanding, measurement input								123.8
January 2021 Private Placement [Member] | January 2021 Purchase Agreement [Member] | Warrants [Member] | Stock Price [Member]
Class Of Warrant Or Right [Line Items]
Warrants and rights outstanding, measurement input								2.88
January 2021 Private Placement [Member] | January 2021 Purchase Agreement [Member] | Warrants [Member] | Risk-Free Interest Rate [Member]
Class Of Warrant Or Right [Line Items]
Warrants and rights outstanding, measurement input								0.5
January 2021 Private Placement [Member] | January 2021 Placement Agent Warrants [Member] | January 2021 Purchase Agreement [Member]
Class Of Warrant Or Right [Line Items]
Warrant issued, shares of common stock called by warrant	393,839
Warrants issued, exercise price | $ / shares	$ 3.99
Warrant, exercisable term	5 years 6 months
Issuance of placement agent warrants | $	$ 942,000
Offering costs | $	1,900,000
January 2021 Private Placement [Member] | January 2021 Placement Agent Warrants [Member] | January 2021 Purchase Agreement [Member] | Warrants [Member]
Class Of Warrant Or Right [Line Items]
Offering costs | $	$ 2,800,000