Warrants - Additional Information (Detail) $ / shares in Units, $ in Millions										4 Months Ended	12 Months Ended
	Dec. 11, 2019 $ / shares	Sep. 12, 2017 $ / shares shares	Sep. 12, 2017 USD ($) $ / shares shares	May 10, 2017 $ / shares shares	Apr. 28, 2017 $ / shares shares	Apr. 28, 2017 USD ($) $ / shares shares	Sep. 26, 2014 $ / shares shares	Sep. 03, 2013	Mar. 22, 2013 USD ($) Investor $ / shares shares	Dec. 14, 2015 shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 shares	Dec. 31, 2013 shares	Aug. 14, 2015 $ / shares	Jan. 17, 2012 $ / shares shares
Class of Warrant or Right [Line Items]
Offering price (in dollars per share) | $ / shares					$ 1.00	$ 1.00
Warrants outstanding									92,277
Warrants exercised (in shares)					0
Reverse stock split, conversion ratio	0.07692307692000
Warrants Not Settleable in Cash
Class of Warrant or Right [Line Items]
Number of warrants outstanding (in shares)													1,012,513
Share-based compensation arrangement | $											$ 0.2	$ 5.3
Minimum
Class of Warrant or Right [Line Items]
Percentage of warrants exercisability											4.99%
Outstanding voting stock acquisition											50.00%
Series A Warrant
Class of Warrant or Right [Line Items]
Warrants, exercise price (in dollars per share) | $ / shares					$ 13.00	13.00
Series B Warrant
Class of Warrant or Right [Line Items]
Warrants, exercise price (in dollars per share) | $ / shares	$ 1.39				$ 13.00	$ 13.00
Warrants exercised (in shares)											0	542,478	684,131
Series B Warrant | Warrants Not Settleable in Cash
Class of Warrant or Right [Line Items]
Number of warrants outstanding (in shares)											1,963,451
Service Warrants | Service Agreements
Class of Warrant or Right [Line Items]
Warrants, exercise price (in dollars per share) | $ / shares		$ 13.00	$ 13.00
Warrant, expiration period (in shares)		10 years
Warrants exercised (in shares)											15,385	50,000
Number of common stock or warrants in each unit		73,076	73,076
Percentage of vesting date of execution agreement			25.00%
Percentage of vesting completion		50.00%
Percentage of vesting achieving			25.00%
Achieving cumulative product revenue | $			$ 15.0
Recognized initial expense | $													$ 0.6
Share-based compensation | $													$ 0.3
Warrants, remaining expense recognized | $												$ 0.3
Common Stock | Series A Warrant
Class of Warrant or Right [Line Items]
Number of common stock or warrants in each unit					0.077	0.077
Common Stock | Series B Warrant
Class of Warrant or Right [Line Items]
Gross proceeds from public offering | $						$ 24.9
Number of common stock or warrants in each unit					0.058	0.058
Common Stock | Series A
Class of Warrant or Right [Line Items]
Gross proceeds from public offering | $						$ 24.9
First Amended SVB Loan Agreement
Class of Warrant or Right [Line Items]
Warrants, exercise price (in dollars per share) | $ / shares							$ 52.20
Warrant, expiration period (in shares)							7 years
Warrants exercised (in shares)											0	2,145		0
Stock issued due to exercise of options												660
Common stock warrants issued							2,948
Second Amended SVB Loan Agreement
Class of Warrant or Right [Line Items]
Warrants, exercise price (in dollars per share) | $ / shares																$ 40.30
Warrant, expiration period (in shares)										7 years
Warrants exercised (in shares)											0	5,211		0
Stock issued due to exercise of options												2,426
Common stock warrants issued										8,684
Stock Purchase Agreement 2013 | 2013 PIPE investors
Class of Warrant or Right [Line Items]
Number of investors | Investor									17
Stock issued, shares									186,092
Offering price (in dollars per share) | $ / shares									$ 16.25
Proceeds from PIPE | $									$ 3.0
Warrants to purchase common shares									93,046
Warrants, exercise price (in dollars per share) | $ / shares									$ 21.45
Warrant, expiration period (in shares)									5 years
Loan and Security Agreement | Term Loan
Class of Warrant or Right [Line Items]
Warrant, expiration period (in shares)				5 years
Warrants exercised (in shares)											0
Loan and Security Agreement | Term Loan | First Tranche
Class of Warrant or Right [Line Items]
Warrants, exercise price (in dollars per share) | $ / shares				$ 13.00
Loan and Security Agreement | Maximum | Term Loan | First Tranche
Class of Warrant or Right [Line Items]
Warrants to purchase common shares				95,750
Related Parties | Stock Purchase Agreement 2013 | 2013 PIPE investors
Class of Warrant or Right [Line Items]
Stock issued, shares									98,462
Warrants to purchase common shares									49,231
Warrants exercised (in shares)												61,538	18,462
Warrants, expirations in period												7,354
Prior Lenders
Class of Warrant or Right [Line Items]
Warrants to purchase common shares																	21,506
Warrants, exercise price (in dollars per share) | $ / shares																	$ 18.85
Warrant, expiration period (in shares)			10 years
Warrants exercised (in shares)												10,753		0	10,753
Stock issued due to exercise of options												8,065			8,674
Merger Agreement
Class of Warrant or Right [Line Items]
Option exchange ratio								0.0887