Fair Value of Financial Instruments (Details) (Recurring basis, USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Total
Liabilities measured at fair value on a recurring basis
Derivative liabilities	$ 201	$ 5,778
(Level 3)
Liabilities measured at fair value on a recurring basis
Derivative liabilities	201	5,778
Series B-1 Preferred Stock | Conversion feature embedded | Total
Liabilities measured at fair value on a recurring basis
Derivative liabilities	26	1,835
Series B-1 Preferred Stock | Conversion feature embedded | (Level 3)
Liabilities measured at fair value on a recurring basis
Derivative liabilities	26	1,835
2008 Warrants | Total
Liabilities measured at fair value on a recurring basis
Derivative liabilities		29
2008 Warrants | (Level 3)
Liabilities measured at fair value on a recurring basis
Derivative liabilities		29
2010 Warrants | Total
Liabilities measured at fair value on a recurring basis
Derivative liabilities	175	3,914
2010 Warrants | (Level 3)
Liabilities measured at fair value on a recurring basis
Derivative liabilities	$ 175	$ 3,914