Stockholders' Equity - Summary of Warrant Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Common shares Issuable upon Exercise
Outstanding at December 31, 2014 (in shares)	6,859,682
Issued (in shares)	3,174,417
Exercised (in shares)	0
Cancelled (in shares)	(1,196,748)
Outstanding as of December 31, 2015 (in shares)	8,837,351	6,859,682
Exercisable at December 31, 2015 (in shares)	8,837,351
Weighted Average Exercise Price
Outstanding at December 31, 2014 (USD per Share)	$ 3.83
Issued (USD per Share)	1.81
Exercised (USD per Share)	0.00
Cancelled (USD per Share)	2.38
Outstanding at December 31, 2015 (USD per Share)	3.30	$ 3.83
Exercisable at December 31, 2015 (USD per Share)	$ 3.30
Weighted Average Contractual Life
Outstanding	3 years 7 months 7 days	2 years 8 months 7 days
Issued	6 years 3 months 7 days
Exercisable at December 31, 2015 (in years)	3 years 7 months 7 days