Stock Options and Stock-based Employee Compensation, Options Outstanding, Vested and Exercisable (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee stock-based compensation	$ 2,411,000	$ 867,000	$ 1,410,000
Modification Compensation Cost	800,000
Weighted-average assumptions used in estimating fair value of stock options [Abstract]
Weighted average expected volatility (in hundredths)	111.00%	113.00%	112.00%
Weighted average expected term	4 years 7 months 6 days	4 years 9 months 18 days	4 years 10 months 24 days
Weighted average risk-free interest rate (in hundredths)	0.74%	1.08%	1.47%
Expected dividends (in hundredths)	0.00%	0.00%	0.00%
Fair value of options vested during period	2,200,000	600,000	1,500,000
Unrecognized compensation cost related to non-vested share-based compensation arrangements	3,400,000
Weighted-average vesting period of stock options	2 years 1 month 6 days
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee stock-based compensation	487,000	289,000	479,000
General & Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee stock-based compensation	$ 1,924,000	$ 578,000	$ 931,000
$1.58 - $156.45 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 1.58
Exercise Price Range, Upper Range Limit	$ 156.45
Outstanding options	3,997
Outstanding, weighted average exercise price (in dollars per share)	$ 11.11
Outstanding, weighted average remaining contractual term	7 years 10 months 24 days
Vested and exercisable options outstanding	1,654
Vested and exercisable options, weighted average exercise price (in dollars per share)	$ 23.53
Vested and exercisable options, weighted average remaining contractual term	6 years 10 months 24 days