Equity Financing - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended					12 Months Ended
	Dec. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020
Maximum [Member]
Class Of Warrant Or Right [Line Items]
Proceeds from issuance, aggregate offering prices						$ 50.0
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					$ 10.7258
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				$ 14.0
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				$ 9.94
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			$ 7.5
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			$ 5.00
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		$ 10.0
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		$ 7.52
Warrants expiration period		5 years 6 months
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	$ 8.0
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					2,618,658
Warrants issued, exercise price	$ 3.00					$ 3.00
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				$ 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			$ 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		$ 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					130,933
Warrants issued, exercise price	$ 3.8188					$ 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					$ 45.75
Warrants expiration period					5 years
Proceeds from issuance of common stock and warrants gross					$ 10.0
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					$ 41.5625
Warrant, exercisable term					5 years