Warrants - Additional Information (Detail) $ / shares in Units, $ in Millions					12 Months Ended
	Aug. 14, 2015 $ / shares shares	Sep. 26, 2014 $ / shares shares	May 22, 2013 USD ($) Investor $ / shares shares	Jan. 17, 2012 $ / shares shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 shares	Jul. 10, 2015 $ / shares	Jun. 11, 2015 $ / shares	Apr. 30, 2014 $ / shares	Apr. 14, 2014 $ / shares	Sep. 03, 2013 shares
Class of Warrant or Right [Line Items]
Stock issued, price per share | $ / shares									$ 3.00	$ 3.00	$ 4.00	$ 4.00
Warrant, expiration period		7 years
Warrants outstanding													1,200,000
Warrants exercised					0
Warrants Not Settleable in Cash [Member]
Class of Warrant or Right [Line Items]
Share-based compensation arrangement by share-based payment award, Equity instruments other than options, aggregate intrinsic value, outstanding | $					$ 0.0	$ 1.0	$ 1.6
Amended Loan Agreement [Member]
Class of Warrant or Right [Line Items]
Warrants, exercise price | $ / shares	$ 3.10	$ 4.015
Warrant, expiration period					7 years
Warrants exercised					0	0	0
Common stock warrants issued	112,903	38,325
Stock Purchase Agreement 2013 [Member] | 2013 PIPE investors [Member]
Class of Warrant or Right [Line Items]
Number of investors | Investor			17
Stock issued, shares			2,420,000
Stock issued, price per share | $ / shares			$ 1.25
Proceeds from PIPE | $			$ 3.0
Warrants to purchase common shares			1,209,600
Warrants, exercise price | $ / shares			$ 1.65
Warrant, expiration period			5 years
Merger Agreement [Member]
Class of Warrant or Right [Line Items]
Exchange ratio													1.1533
Related Parties [Member] | Stock Purchase Agreement 2013 [Member] | 2013 PIPE investors [Member]
Class of Warrant or Right [Line Items]
Stock issued, shares			1,280,000
Warrants to purchase common shares			640,000
Warrants exercised						0	10,000
Silicon Valley Bank and Oxford Finance LLC [Member]
Class of Warrant or Right [Line Items]
Warrants to purchase common shares				279,588
Warrants, exercise price | $ / shares				$ 1.45
Warrant, expiration period				10 years
Warrants exercised					0	0	0	139,794
Stock issued due to exercise of options								112,766