Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended	12 Months Ended
	Aug. 02, 2019	Mar. 08, 2018	Dec. 31, 2011	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2019	Mar. 31, 2018
Subsidiary Sale Of Stock [Line Items]
Net proceeds from offering					$ 1,977	$ 51,902
Redeemable preferred stock carrying value					$ 23,603	$ 23,603
Redeemable preferred stock authorized					20,000,000	20,000,000
Redeemable preferred stock, price per share					$ 0.0001	$ 0.0001
Preferred stock convertible to common stock								14,300,000
Warrant outstanding					26,557,180
Stock-based compensation					$ 10,956	$ 5,304
Patrick S. Miles
Subsidiary Sale Of Stock [Line Items]
Number of warrants issued (in shares)						1,327,434
Exercise price of warrants						$ 5
Warrant expiration period						5 years
Stock-based compensation						$ 1,400
SiliconValley Bank (SVB)
Subsidiary Sale Of Stock [Line Items]
Number of warrants issued (in shares)			7,812
Exercise price of warrants			$ 19.20
Amendment fee amount waived			$ 200
Warrant term			10 years
Squadron Capital
Subsidiary Sale Of Stock [Line Items]
Number of warrants issued (in shares)						845,000	4,838,710
Exercise price of warrants						$ 3.15	$ 2.17
Warrant outstanding							5,683,710
Warrant expiration period						7 years
2017 Common Stock Warrants
Subsidiary Sale Of Stock [Line Items]
Exercise price of warrants					$ 2.00
Warrant outstanding					3,232,000
Proceeds from exercise of warrant					$ 1,100	$ 4,000
Number of warrants exercised					500,000	1,900,000
2017 Common Stock Warrants | Maximum
Subsidiary Sale Of Stock [Line Items]
Beneficial ownership limitation percentage					4.99%
Beneficial ownership, limitation option, percentage					9.99%
Beneficial ownership limitation notification period					61 days
2017 Banker Warrants
Subsidiary Sale Of Stock [Line Items]
Exercise price of warrants					$ 2.50
Warrant outstanding					148,554
2018 Common Stock Warrants
Subsidiary Sale Of Stock [Line Items]
Number of warrants issued (in shares)					1,800,000
Exercise price of warrants					$ 3.50
Warrant outstanding					13,770,488
Warrant expiration period					5 years
2018 Common Stock Warrants | Maximum
Subsidiary Sale Of Stock [Line Items]
Beneficial ownership limitation percentage					4.99%
Beneficial ownership, limitation option, percentage					9.99%
Beneficial ownership limitation notification period					61 days
Redeemable Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Redeemable preferred stock carrying value					$ 23,600	$ 23,600
Redeemable preferred stock authorized					20,000,000	20,000,000
Redeemable preferred stock redemption, price per share					$ 9.00	$ 9.00
Redeemable preferred stock, price per share					$ 7.11	$ 7.11
Series A Convertible Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Number of preferred shares converted					3,909	1,274
Number of preferred shares outstanding for being conversion					135
Common Stock
Subsidiary Sale Of Stock [Line Items]
Common stock issued					12,535,000
Number of preferred shares converted to common stock					1,954,000	14,986,000
Common Stock | Series A Convertible Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Number of preferred shares converted to common stock					1,954,334	636,997
Number of preferred shares outstanding for being conversion to common stock					67,338
August 2019 Offering
Subsidiary Sale Of Stock [Line Items]
Net proceeds from offering	$ 53,900
August 2019 Offering | Common Stock
Subsidiary Sale Of Stock [Line Items]
Common stock issued	12,535,000
Shares issued price per share	$ 4.60
Shares issued of underwriters option to purchase additional shares	1,635,000
2017 Private Placement | 2017 Common Stock Warrants
Subsidiary Sale Of Stock [Line Items]
Exercise price of warrants					$ 2.00
2017 Private Placement | 2017 Banker Warrants
Subsidiary Sale Of Stock [Line Items]
Exercise price of warrants					$ 2.50
2017 Private Placement | 2017 Banker Warrants | Maximum
Subsidiary Sale Of Stock [Line Items]
Number of warrants issued (in shares)					471,600
2017 Private Placement | Series A Convertible Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Shares issued price per share				$ 1,000
Preferred stock, shares issued				15,245
2017 Private Placement | Common Stock
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock upon securities purchase agreement				1,809,628
Common stock purchase price per share				$ 2.00
2017 Private Placement | Common Stock | 2017 Common Stock Warrants | Maximum
Subsidiary Sale Of Stock [Line Items]
Number of warrants issued (in shares)					9,432,000
2017 Private Placement | Common Stock | Series A Convertible Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock convertible to common stock				7,622,372
2018 Private Placement
Subsidiary Sale Of Stock [Line Items]
Exercise price of warrants		$ 3.50
Warrant expiration period		5 years
Aggregate gross proceeds for private placement		$ 45,200
2018 Private Placement | 2017 Common Stock Warrants
Subsidiary Sale Of Stock [Line Items]
Exercise price of warrants		$ 2.00
Warrant outstanding		2,400,000
Proceeds from exercise of warrant						$ 4,800
2018 Private Placement | 2017 Banker Warrants
Subsidiary Sale Of Stock [Line Items]
Warrant outstanding					148,554
Proceeds from exercise of warrant					$ 100	$ 800
Number of warrants exercised					18,864	304,182
2018 Private Placement | 2018 Common Stock Warrants
Subsidiary Sale Of Stock [Line Items]
Warrant outstanding					13,770,488
Proceeds from exercise of warrant					$ 600
Number of warrants exercised					200,000	0
2018 Private Placement | Series A Convertible Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Shares issued price per share		$ 1,000
Preferred stock, shares issued		45,200
2018 Private Placement | Common Stock | Maximum
Subsidiary Sale Of Stock [Line Items]
Number of warrants issued (in shares)		12,196,851
2018 Private Placement | Common Stock | Series A Convertible Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock convertible to common stock		14,349,236