Consolidated Statements of Changes in Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital [Member]	Accumulated Deficit	Total
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2012	$ 1	$ 40,842	$ (43,153)	$ (2,310)
Beginning Balance, (in shares) at Dec. 31, 2012	16,470,281
Share-based compensation expense		3,136		3,136
Issuance of common stock upon exercise of warrants		15,952		15,952
Issuance of common stock upon exercise of warrants (in shares)	3,056,211
Issuance of common stock upon exercise of stock options		455		455
Issuance of common stock upon exercise of stock options (in shares)	147,221
Fair value of derivative warrant liability reclassified to additional paid-in capital		33,456		33,456
Incremental fair value from warrant modification		765		765
Issuance of common stock to 401(k) plan (in dollars)		192		192
Issuance of common stock to 401(k) plan (in shares)	19,721
Net loss			(38,756)	(38,756)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2013	$ 1	94,798	(81,909)	12,890
Ending Balance, (in shares) at Dec. 31, 2013	19,693,434
Share-based compensation expense		2,730		2,730
Issuance of common stock in public offerings		7,770		7,770
Issuance of stock (in shares)	3,500,312
Issuance of stock for services		477		477
Issuance of stock for services (in shares)	74,626
Issuance of common stock upon exercise of warrants		12		12
Issuance of common stock upon exercise of warrants (in shares)	9,975
Issuance of common stock upon exercise of stock options		212		212
Issuance of common stock upon exercise of stock options (in shares)	132,900
Issuance of common stock to 401(k) plan (in dollars)		173		173
Issuance of common stock to 401(k) plan (in shares)	41,753
Net loss			(18,346)	(18,346)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2014	$ 1	106,172	(100,255)	5,918
Ending Balance, (in shares) at Dec. 31, 2014	23,453,000
Share-based compensation expense		4,666		4,666
Issuance of common stock in public offerings		14,480		14,480
Issuance of stock (in shares)	2,388,245
Issuance of common stock upon exercise of warrants		7,789		7,789
Issuance of common stock upon exercise of warrants (in shares)	1,379,575
Issuance of common stock upon exercise of stock options		1,068		1,068
Issuance of common stock upon exercise of stock options (in shares)	316,177
Fair value of derivative warrant liability reclassified to additional paid-in capital		16,121		16,121
Fractional shares issued due to reverse stock split	1,514
Issuance of common stock to 401(k) plan (in dollars)		201		201
Issuance of common stock to 401(k) plan (in shares)	17,437
Net loss			(33,314)	(33,314)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2015	$ 1	$ 150,497	$ (133,569)	$ 16,929
Ending Balance, (in shares) at Dec. 31, 2015	27,555,948