Stockholders' Equity - Common and Preferred Shares - Summary of Company's Outstanding Common Stock Warrants (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 25, 2015	Dec. 31, 2014
Class of Warrant or Right [Line Items]
Exercise Price		$ 1.7125
Number of warrants	10,599		7,445
Private Placement Series A Warrants [Member]
Class of Warrant or Right [Line Items]
Date of Issuance	Apr. 16, 2013
Warrant Term	5 years
Exercise Price	$ 3.40
Number of warrants	1,460		1,460
Private Placement Series B Warrants [Member]
Class of Warrant or Right [Line Items]
Date of Issuance	Apr. 16, 2013
Warrant Term	2 years
Exercise Price	$ 3.40
Number of warrants	757		757
2013 Private Placement Warrants [Member]
Class of Warrant or Right [Line Items]
Date of Issuance	Sep. 23, 2013
Warrant Term	5 years
Exercise Price	$ 2.24
2013 Private Placement Warrants [Member]
Class of Warrant or Right [Line Items]
Date of Issuance	Sep. 23, 2013
Warrant Term	5 years
Exercise Price	$ 2.80
Number of warrants	147		147
2014 Public Offering Warrants [Member]
Class of Warrant or Right [Line Items]
Date of Issuance	Feb. 18, 2014
Warrant Term	5 years
Exercise Price	$ 2.75
Number of warrants	1,872		1,872
2014 Public Offering Warrants [Member]
Class of Warrant or Right [Line Items]
Date of Issuance	Feb. 18, 2014
Warrant Term	5 years
Exercise Price	$ 2.56
Number of warrants	293		293
2014 Private Placement Warrants [Member]
Class of Warrant or Right [Line Items]
Date of Issuance	May 28, 2014
Warrant Term	5 years 3 months
Exercise Price	$ 2.90
Number of warrants	2,700		2,700
2014 Private Placement Warrants [Member]
Class of Warrant or Right [Line Items]
Date of Issuance	May 28, 2014
Warrant Term	5 years 3 months
Exercise Price	$ 3.70
Number of warrants	216		216
2015 Private Placement Warrants [Member]
Class of Warrant or Right [Line Items]
Date of Issuance	Mar. 25, 2015
Warrant Term	5 years
Exercise Price	$ 1.71
Number of warrants	2,920
2015 Private Placement Warrants [Member]
Class of Warrant or Right [Line Items]
Date of Issuance	Mar. 25, 2015
Warrant Term	2 years 3 months
Exercise Price	$ 2.13
Number of warrants	234