Consolidated Statements of Stockholders' Equity (Deficit) (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Subscription receivable	Additional paid-in capital	Accumulated deficit	Non-controlling interest
Balance at Dec. 31, 2011	$ (16,268)	$ 4	$ (550)	$ 27,081	$ (43,271)	$ 468
Balance (shares) at Dec. 31, 2011		3,827,132
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from equity financing, net	40,185	18	(2,004)	42,171
Proceeds from equity financing, net (in shares)		18,203,000
Fair value of warrants issued with financing	1,098			1,098
Preferred stock series D and E converted	1,350	2		1,348
Preferred stock series D and E converted (in shares)		2,021,120
Conversion of notes payable	2,385	1		2,384
Conversion of notes payable (in shares)		898,641
Issuance of common stock	6,917	1		6,916
Issuance of common stock (in shares)		1,317,520
Cancellation of certificate	0		550	(550)
Cancellation of certificate (in shares)		(40,000)
Exercise of warrants	10			10
Exercise of warrants (in shares)		2,496
Stock-based compensation expense	1,224			1,224
Net loss	(12,711)				(12,243)	(468)
Balance at Dec. 31, 2012	24,190	26	(2,004)	81,682	(55,514)	0
Balance (shares) at Dec. 31, 2012		26,229,909
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from equity financing, net	47,118	12	0	47,106
Proceeds from equity financing, net (in shares)		12,311,698
Subscription received	2,004		2,004
Issuance of common stock	6,406	2		6,404
Issuance of common stock (in shares)		1,243,781
Exercise of warrants	352			352
Exercise of warrants (in shares)		46,837
Stock-based compensation expense	1,150			1,150
Net loss	(31,554)				(31,554)
Balance at Dec. 31, 2013	49,666	40	0	136,694	(87,068)	0
Balance (shares) at Dec. 31, 2013		39,832,225
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock	5,154	1		5,153
Issuance of common stock (in shares)		1,024,590
Stock-based compensation expense	1,239			1,239
Net loss	(25,650)				(25,650)
Balance at Dec. 31, 2014	$ 30,409	$ 41	$ 0	$ 143,086	$ (112,718)	$ 0
Balance (shares) at Dec. 31, 2014		40,856,815