Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		12 Months Ended
	Mar. 08, 2018	Dec. 31, 2011	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Subsidiary Sale Of Stock [Line Items]
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					22,301,515
Stock-based compensation					$ 5,304	$ 3,981
Squadron Capital
Subsidiary Sale Of Stock [Line Items]
Number of warrants issued (in shares)					845,000
Exercise price of warrants					$ 3.15
Warrant expiration period					7 years
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
Patrick S. Miles | Risk-free Interest Rate
Subsidiary Sale Of Stock [Line Items]
Warrants and rights outstanding measurement input					0.019
Patrick S. Miles | Volatility
Subsidiary Sale Of Stock [Line Items]
Warrants and rights outstanding measurement input					0.995
Patrick S. Miles | Expected Term
Subsidiary Sale Of Stock [Line Items]
Warrants term					2 years 3 months 18 days
Patrick S. Miles | Dividend Yield
Subsidiary Sale Of Stock [Line Items]
Warrants and rights outstanding measurement input					0.00
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
2017 Common Stock Warrants
Subsidiary Sale Of Stock [Line Items]
Exercise price of warrants					$ 2.00
Warrant outstanding					3,757,000
Proceeds from exercise of warrant					$ 4,000	$ 3,300
Number of warrants exercised					1,900,000	1,700,000
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 Common Stock Warrants | Minimum
Subsidiary Sale Of Stock [Line Items]
Percentage of outstanding voting stock acquired					50.00%
2017 Banker Warrants
Subsidiary Sale Of Stock [Line Items]
Exercise price of warrants					$ 2.50
Warrant outstanding					167,418
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					13,996,851
2018 Common Stock Warrants | Minimum
Subsidiary Sale Of Stock [Line Items]
Percentage of outstanding voting stock acquired					50.00%
Common Stock
Subsidiary Sale Of Stock [Line Items]
Number of preferred shares converted to common stock					14,986,000	4,964,000
2017 Private Placement
Subsidiary Sale Of Stock [Line Items]
Aggregate gross proceeds for private placement				$ 18,900
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 | 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
2018 Private Placement
Subsidiary Sale Of Stock [Line Items]
Aggregate gross proceeds for private placement	$ 45,200
Exercise price of warrants	$ 3.50
Proceeds from exercise of warrant			$ 4,800
Warrant expiration period	5 years
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					167,418
Proceeds from exercise of warrant					$ 800
Number of warrants exercised					304,182	0
2018 Private Placement | Common Stock | Maximum
Subsidiary Sale Of Stock [Line Items]
Number of warrants issued (in shares)	12,196,851
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]
Percentage of outstanding preferred stock shares				75.00%
Number of preferred shares converted					1,274	9,927
Number of preferred shares outstanding for being conversion					4,043
Series A Convertible Preferred Stock | Common Stock
Subsidiary Sale Of Stock [Line Items]
Number of preferred shares converted to common stock					636,997	4,963,702
Number of preferred shares outstanding for being conversion to common stock					2,021,673
Series A Convertible Preferred Stock | 2017 Private Placement
Subsidiary Sale Of Stock [Line Items]
Preferred stock, shares issued				15,245
Shares issued price per share				$ 1,000
Series A Convertible Preferred Stock | 2017 Private Placement | Common Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock convertible to common stock				7,622,372
Series A Convertible Preferred Stock | 2018 Private Placement
Subsidiary Sale Of Stock [Line Items]
Preferred stock, shares issued	45,200
Shares issued price per share	$ 1,000
Series A Convertible Preferred Stock | 2018 Private Placement | Common Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock convertible to common stock	14,349,236