Statements of Stockholders' Equity (Deficit) (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Comprehensive Income
Balance at Dec. 31, 2009	$ 2,512	$ 124	$ 11,556	$ (9,201)	$ 33
Balance (in shares) at Dec. 31, 2009		12,398,919
Comprehensive loss
Net loss	(10,892)			(10,892)		(10,892)
Unrealized gain (loss) on investments, net	13				13	13
Reclassification of unrealized gain on short-term investments	(46)				(46)	(46)
Comprehensive loss	(10,925)					(10,925)
Common stock issued upon exercise of investor stock purchase option	7,000	10	6,990
Common stock issued upon exercise of investor stock purchase option (in shares)		1,000,000
Common stock issued, $7.00 per share, under private placement offering (net of issuance costs of $44)	1,236	2	1,234
Common stock issued, $7.00 per share, under private placement offering (net of issuance costs of $44) (in shares)		182,872
Stock-based compensation expense	625		625
Balance at Dec. 31, 2010	448	136	20,405	(20,093)
Balance (in shares) at Dec. 31, 2010		13,581,791
Comprehensive loss
Net loss	(4,250)			(4,250)		(4,250)
Unrealized gain (loss) on investments, net	(3)				(3)	(3)
Comprehensive loss	(4,253)					(4,253)
Issuance of common stock in public offering, net of issuance costs	13,632	20	13,612
Issuance of common stock in public offering, net of issuance costs (in shares)		2,062,500
Issuance of common stock to Aspire Capital		4	(4)
Issuance of common stock to Aspire Capital (in shares)		378,788
Restricted stock grants		1	(1)
Restricted stock grants (in shares)		135,000
Stock-based compensation expense	492		492
Exercise of stock options	88	1	87
Exercise of stock options (in shares)		87,500
Balance at Dec. 31, 2011	10,407	162	34,591	(24,343)	(3)
Balance (in shares) at Dec. 31, 2011	16,245,579	16,245,579
Comprehensive loss
Net loss	(5,507)			(5,507)		(5,507)
Unrealized gain (loss) on investments, net	3				3	3
Comprehensive loss	(5,504)					(5,504)
Common stock issued under common stock purchase agreement	135	1	134
Common stock issued under common stock purchase agreement (in shares)		100,000
Issuance of common stock in public offering, net of issuance costs	5,441	100	5,341
Issuance of common stock in public offering, net of issuance costs (in shares)		10,000,000
Stock-based compensation expense	588		588
Exercise of stock options	1		1
Exercise of stock options (in shares)		500
Balance at Dec. 31, 2012	$ 11,068	$ 263	$ 40,655	$ (29,850)
Balance (in shares) at Dec. 31, 2012	26,346,079	26,346,079