Stockholders' Equity - Additional Information (Detail)														1 Months Ended	12 Months Ended
	Dec. 21, 2021 USD ($) $ / shares shares	Dec. 02, 2021 USD ($) $ / shares shares	Nov. 30, 2021 USD ($) shares	Nov. 26, 2021 USD ($) $ / shares shares	Nov. 24, 2021 USD ($) shares	Dec. 17, 2020 USD ($) $ / shares shares	Jul. 17, 2020 shares	Jul. 16, 2020 shares	Apr. 10, 2020 USD ($) d $ / shares shares	Dec. 12, 2019 USD ($) $ / shares shares	Mar. 08, 2018 $ / shares shares	Sep. 30, 2016 $ / shares shares	Jun. 21, 2016 $ / shares shares	Jun. 30, 2021 USD ($) shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 shares	Jun. 18, 2019 shares	Jun. 17, 2019 shares	May 07, 2014 $ / shares shares
Schedule Of Capitalization Equity [Line Items]
Common stock, par value (in dollars per share) | $ / shares															$ 0.001	$ 0.001
Common stock, shares authorized (in shares)							100,000,000	250,000,000							100,000,000	100,000,000		250,000,000	125,000,000
Common stock, shares issued (in shares)							10,508,302	105,083,291							28,705,334	19,663,698
Common stock, shares outstanding (in shares)							10,508,302	105,083,291							28,705,334	19,663,698
Common stock, reverse stock split															1-for-10
Reverse stock split, ratio								0.1
Stock issued during period as result of reverse stock splits							0	0
Preferred stock, shares authorized (in shares)															5,000,000	5,000,000				5,000,000
Preferred stock, par value (in dollars per share) | $ / shares															$ 0.001	$ 0.001				$ 0.001
Preferred stock, shares issued (in shares)															0	0
Preferred stock, shares outstanding (in shares)															0	0
Common stock issued, net of expenses (in shares)											1,775,150		937,500
Proceeds from common stock issued | $															$ 38,552,000	$ 90,554,000
Warrant liabilities fair value adjustment | $															(30,365,000)	5,214,000
Warrant liabilities | $															18,062,000	33,592,000
Common stock issued, net of expenses | $															41,040,000	$ 57,184,000
Warrant liabilities | $															$ 18,100,000
Increase in sale of common stock maximum number of share sold per business day									200,000
Warrants to purchase common stock associated with Danforth Advisors
Schedule Of Capitalization Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)															50,000
Exercise price of warrants (in dollars per share) | $ / shares															$ 5.50
Warrant expiration period															5 years
Warrants to purchase common stock associated with Loan Agreement
Schedule Of Capitalization Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)												12,243
Exercise price of warrants (in dollars per share) | $ / shares												$ 36.754
Warrants, expiration date												Sep. 30, 2021
Warrant expiration period												5 years
Aspire Capital | Common Stock Purchase Agreement
Schedule Of Capitalization Equity [Line Items]
Common stock issued, net of expenses (in shares)															400,000
Proceeds from common stock issued | $															$ 2,600,000
Number of purchase aggregate shares of common stock									1,956,547
Percentage of common stock outstanding									19.99%
Number of shares committed									70,910
Average purchase price of shares sold | $ / shares									$ 8.461
Percentage of common stock owned									19.99%
Sale of common stock maximum number of share sold per business day									25,000
Stock purchase price average number of trading days lowest closing sales price out of consecutive trading days | d									3
Stock purchase price number of consecutive trading days | d									10
Percentage of purchase price per share									97.00%
Option to Purchase Common Stock
Schedule Of Capitalization Equity [Line Items]
Options expiration date										2020-01
Maximum | Aspire Capital | Common Stock Purchase Agreement
Schedule Of Capitalization Equity [Line Items]
Public offering price | $ / shares									$ 0.25
Sale of common stock at sole discretion | $									$ 20,000,000.0
Stock purchase percentage on aggregate shares of common stock traded									30.00%
Maximum | Option to Purchase Common Stock
Schedule Of Capitalization Equity [Line Items]
Number of options not exercised										583,333
Series 1 Warrant
Schedule Of Capitalization Equity [Line Items]
Proceeds from warrant exercised | $	$ 21,100,000				$ 1,200,000
Class of warrant or right exercised	3,370,800
Warrant liabilities fair value adjustment | $	$ 1,900,000				100,000
Fair value earnings | $	1,400,000
Contractual liability value | $	$ 1,900,000				$ 100,000
Investor provided conversion notice					160,000
Warrant liabilities | $					$ 100,000
Series 1 Warrant | Maximum
Schedule Of Capitalization Equity [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares	$ 6.25
Class of warrant or right outstanding	6,100,000
Series 1 Warrant | Minimum
Schedule Of Capitalization Equity [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares	$ 6.25
Class of warrant or right outstanding	5,980,800
Common Stock
Schedule Of Capitalization Equity [Line Items]
Common stock, shares outstanding (in shares)															28,705,334	19,663,698	9,741,372
Common stock issued, net of expenses (in shares)															8,067,562	9,156,304
Common stock issued, net of expenses | $															$ 11,000	$ 9,000
Warrant liability
Schedule Of Capitalization Equity [Line Items]
Proceeds from warrant exercised | $	$ 14,900,000
Class of warrant or right, unissued	2,390,000
Warrants held percentage	5.00%
Commitment Shares | Aspire Capital | Common Stock Purchase Agreement
Schedule Of Capitalization Equity [Line Items]
Common stock shares issued									70,910
Commitment Shares | Aspire Capital | Common Stock Purchase Agreement | Other Expense
Schedule Of Capitalization Equity [Line Items]
Fair value of shares | $															$ 600,000
December 2020 Public Offering
Schedule Of Capitalization Equity [Line Items]
Common stock, par value (in dollars per share) | $ / shares						$ 0.001
Common stock issued, net of expenses (in shares)						8,340,000
Number of warrants issued to purchase common stock (in shares)															2,060,000
Pre-funded warrants were exercised for proceeds | $						$ 2,000,000
Exercise price of warrants (in dollars per share) | $ / shares						$ 0.001
Number of shares received per warrant (in shares)						6,800,000
Proceeds from common stock issued | $						$ 79,500,000
Warrant liabilities fair value adjustment | $															$ 1,900,000
December 2020 Public Offering | Pre-funded Warrants
Schedule Of Capitalization Equity [Line Items]
Common stock, par value (in dollars per share) | $ / shares						$ 0.001
Number of warrants issued to purchase common stock (in shares)						5,260,000									5,260,000	5,260,000
Public offering price | $ / shares						$ 6.249
December 2020 Public Offering | Series 1 Warrant
Schedule Of Capitalization Equity [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares						$ 7.33
Warrant term						1 year
Number of warrants exercised														360,134
Proceeds from warrant exercised | $														$ 2,600,000
December 2020 Public Offering | Series 1 Warrant | Maximum
Schedule Of Capitalization Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)						13,600,000
December 2020 Public Offering | Series 2 Warrant
Schedule Of Capitalization Equity [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares						$ 8.25
Warrant term						3 years 6 months
December 2020 Public Offering | Series 2 Warrant | Minimum
Schedule Of Capitalization Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)						5,260,000
December 2020 Public Offering | Common Stock
Schedule Of Capitalization Equity [Line Items]
Public offering price | $ / shares						$ 6.25
December 2019 Public Offering
Schedule Of Capitalization Equity [Line Items]
Common stock issued, net of expenses (in shares)										3,888,888
Number of warrants issued to purchase common stock (in shares)										3,888,888
Exercise price of warrants (in dollars per share) | $ / shares				$ 6.50						$ 11.0
Proceeds from warrant exercised | $			$ 7,200,000
Class of warrant or right outstanding		111,111		1,111,111
Class of warrant or right exercised			1,111,111
Warrants held percentage				5.00%
Warrant liabilities fair value adjustment | $															$ 1,000,000.0
Contractual liability value | $		$ 19,000		$ 200,000
Share price (in dollars per share) | $ / shares										$ 9.00
Common stock issued, net of expenses | $										$ 32,500,000
Warrants, expiration date										Jun. 12, 2023
Class of warrants derecognized		111,111	1,111,111
December 2019 Public Offering | Series 1 Warrant
Schedule Of Capitalization Equity [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares		$ 6.50
Proceeds from warrant exercised | $		$ 700,000
Class of warrant or right exercised		111,111
Fair value earnings | $		$ 18,000
December 2019 Public Offering | Series 1 Warrant | Common Share 1
Schedule Of Capitalization Equity [Line Items]
Class of warrant or right outstanding		361,111
December 2019 Public Offering | Series 1 Warrant | Common Share 2
Schedule Of Capitalization Equity [Line Items]
Class of warrant or right outstanding		827,777
December 2019 Public Offering | Series 1 Warrant | Common Share 3
Schedule Of Capitalization Equity [Line Items]
Class of warrant or right outstanding		194,444
December 2019 Public Offering | Series 1 Warrant | Common Share 4
Schedule Of Capitalization Equity [Line Items]
Class of warrant or right outstanding		111,111
December 2019 Public Offering | Series 2 Warrant
Schedule Of Capitalization Equity [Line Items]
Class of warrant or right exercised		111,111
Contractual liability value | $		$ 19,000
Underwriters | Maximum
Schedule Of Capitalization Equity [Line Items]
Option to purchase shares of common stock										583,333
Underwriters | Warrant liability
Schedule Of Capitalization Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)										583,333
Number of warrants exercised										583,333
March 2018 Public Offering
Schedule Of Capitalization Equity [Line Items]
Public offering price | $ / shares											$ 16.90
March 2018 Public Offering | Series 1 Warrant
Schedule Of Capitalization Equity [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares											$ 18.5
Number of shares received per warrant (in shares)											0.75
Warrant term											371 days
March 2018 Public Offering | Series 1 Warrant | Maximum
Schedule Of Capitalization Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)											1,331,370
March 2018 Public Offering | Series 2 Warrant
Schedule Of Capitalization Equity [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares											$ 20.0
Number of shares received per warrant (in shares)											0.45
Warrant term											5 years
March 2018 Public Offering | Series 2 Warrant | Maximum
Schedule Of Capitalization Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)											798,810
March 2018 Public Offering | Warrant liability | Maximum
Schedule Of Capitalization Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)											2,130,180
June 2016 Public Offering
Schedule Of Capitalization Equity [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares													$ 30.0
Number of shares received per warrant (in shares)													0.45
Warrants, expiration date													Jun. 30, 2021
Warrant expiration period													5 years
June 2016 Public Offering | Warrant liability | Maximum
Schedule Of Capitalization Equity [Line Items]
Number of warrants issued to purchase common stock (in shares)													421,867