Basis of Presentation - Summary of Impact of Correction of Stock Based Compensation Adjustment on Unaudited Interim Financial Statements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Change In Accounting Estimate [Line Items]
Fair value of liability classified stock options	$ 6,298
Additional paid-in capital	29,083		$ 30,346
Accumulated deficit	(112,930)		(103,734)
General and administrative	1,571	$ 1,300
Loss from operations	(6,137)	1,032
Net income (loss)	(9,156)	1,373	$ 13,018
Net loss attributable to common shareholders	$ (9,156)
Net loss per common share - basic and diluted	$ (0.64)
Comprehensive loss	$ (9,156)	464
Stock-based compensation	5,219	186
General and Administrative [Member]
Change In Accounting Estimate [Line Items]
General and administrative - stock based compensation	5,149	$ 136
Scenario, Previously Reported
Change In Accounting Estimate [Line Items]
Additional paid-in capital	30,450
Accumulated deficit	(107,999)
General and administrative	1,789
Loss from operations	(1,206)
Net income (loss)	(4,225)
Net loss attributable to common shareholders	$ (4,225)
Net loss per common share - basic and diluted	$ (0.30)
Comprehensive loss	$ (4,225)
Stock-based compensation	288
Reclassification
Change In Accounting Estimate [Line Items]
General and administrative	(218)
Reclassification | General and Administrative [Member]
Change In Accounting Estimate [Line Items]
General and administrative - stock based compensation	218
Scenario, Adjustment
Change In Accounting Estimate [Line Items]
Fair value of liability classified stock options	6,298
Additional paid-in capital	(1,367)
Accumulated deficit	(4,931)
Loss from operations	(4,931)
Net income (loss)	(4,931)
Net loss attributable to common shareholders	$ (4,931)
Net loss per common share - basic and diluted	$ (0.34)
Comprehensive loss	$ (4,931)
Stock-based compensation	4,931
Scenario, Adjustment | General and Administrative [Member]
Change In Accounting Estimate [Line Items]
General and administrative - stock based compensation	$ 4,931