Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2012

Fair Value of Financial Instruments [Abstract]

Estimated fair values of the liabilities measured on a recurring basis

	Fair Value Measurements at September 30, 2012
	Balance at September  30, 2012		Quoted Prices in Active  Markets (Level 1)		Significant  Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Embedded derivative liabilities	$	3,900	$	—	$	—	$	3,900
Warrant derivative liabilities		8,817		—		—		8,817
Total	$	12,717	$	—	$	—	$	12,717

	Fair Value Measurements at December 31, 2011
	Balance at December 31, 2011		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Embedded derivative liabilities	$	3,680	$	—	$	—	$	3,680
Warrant derivative liabilities		11,590		—		—		11,590
Total	$	15,270	$	—	$	—	$	15,270

Liabilities measured at estimated fair value using unobservable inputs

	Fair Value Measurements Using Significant Unobservable Inputs (Levels 3)
	Embedded  Derivative Liabilities		Warrant  Derivative Liabilities			Total
Beginning balance at December 31, 2011	$	3,680	$	11,590		$	15,270
Adjustment to estimated fair value		77		(2,773	)		(2,696	)
Accrued dividends payable in Series C-1 2 Preferred		143		—			143
Ending balance at September 30, 2012	$	3,900	$	8,817		$	12,717

	Fair Value Measurements Using Significant Unobservable Inputs (Levels 3)
	Embedded  Derivative Liabilities			Warrant Derivative Liabilities			Total
Beginning balance at December 31, 2010	$	5,170		$	932		$	6,102
Adjustment to estimated fair value		(1,620	)		(1,726	)		(3,346	)
Decrease of the embedded derivative liabilities for preferred shares converted into common stock		(315	)		—			(315	)
Forfeited accrued dividends payable in Series C-1 2 Preferred		(72	)		—			(72	)
Accrued dividends payable in Series C-1 1 Preferred		3			—			3
Ending balance at September 30, 2011	$	3,166		$	(794	)	$	2,372