Consolidated Statements of Stockholders' Equity (USD $)	Total	Common Stock	Additional Paid-in Capital	Retained Deficit	Treasury Stock
Balance at Dec. 31, 2009	$ 40,077,441	$ 1,716,416	$ 245,029,557	$ (205,955,693)	$ (712,839)
Balance (in shares) at Dec. 31, 2009		17,164,162.2			42,169
Increase (Decrease) in Stockholders' Equity
Issuance of officer restricted stock units		371	(371)
Issuance of officer restricted stock units (in shares)		3,705.2
Shares issued through ESPP	122,668	4,364	118,304
Shares issued through ESPP (in shares)		43,637.2
Stock-based compensation	858,467		858,467
Warrants issued to service provider	15,739		15,739
Redeemable preferred stock converted to common stock	703,061	30,158	672,903
Redeemable preferred stock converted to common stock (in shares)		301,577.7
Redeemable preferred stock redeemed for common stock	1,317,522	59,887	1,257,635
Redeemable preferred stock redeemed for common stock (in shares)		598,874.1
Stock issued for dividends on redeemable preferred stock	78,826	3,582	75,244
Stock issued for dividends on redeemable preferred stock (in shares)		35,821.9
Issuance of stock for cash, net of issuance costs	2,237,764	99,296	2,138,468
Issuance of stock for cash, net of issuance costs (in shares)		992,963.0
Warrant exercises	5,902,038	182,679	5,719,359
Warrant exercises (in shares)		1,826,787.5
Rounding for fractional shares (in shares)		0.2
Adjust par value for reverse stock split		(1,887,078)	1,887,078
Net loss	(22,679,766)			(22,679,766)
Balance at Dec. 31, 2010	28,633,760	209,675	257,772,383	(228,635,459)	(712,839)
Balance (in shares) at Dec. 31, 2010		20,967,529.0			42,169
Increase (Decrease) in Stockholders' Equity
Issuance of officer restricted stock units		27	(27)
Issuance of officer restricted stock units (in shares)		2,633.0
Shares issued through ESPP	43,244	301	42,943
Shares issued through ESPP (in shares)		30,104.0
Stock-based compensation	724,249		724,249
Redeemable preferred stock converted to common stock	10,611,809	41,409	10,570,400
Redeemable preferred stock converted to common stock (in shares)		4,140,843.8
Redeemable preferred stock redeemed for common stock	4,419,415	20,200	4,399,215
Redeemable preferred stock redeemed for common stock (in shares)		2,020,022.2
Stock issued for dividends on redeemable preferred stock	122,233	608	121,625
Stock issued for dividends on redeemable preferred stock (in shares)		60,699.5
Issuance of stock for cash, net of issuance costs	(21,729)		(21,729)
Warrant exercises	1,497,556	8,853	1,488,703
Warrant exercises (in shares)		885,486.6
Rounding for fractional shares (in shares)		(0.1)
Net loss	(17,018,451)			(17,018,451)
Balance at Jun. 30, 2011	$ 29,012,086	$ 281,073	$ 275,097,762	$ (245,653,910)	$ (712,839)
Balance (in shares) at Jun. 30, 2011		28,107,318.0			42,169