Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2012

Fair Value Measurements [Abstract]

Company's financial assets and liability measured at fair value on a recurring basis

	Fair value measurement using
	Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)		Total
At December 31, 2012
Liabilities
Warrant liability	$	—	$	—	$	374	$	374
Derivative liability		—		—		—		—
Total	$	—	$	—	$	374	$	374

	Fair value measurement using
	Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)		Total
At December 31, 2011
Liabilities
Warrant liability	$	—	$	—	$	13,087	$	13,087
Derivative liability		—		—		534		534
Total	$	—	$	—	$	13,621	$	13,621

Reconciliation of warrant liability measured at fair value on a recurring basis

	Warrant Liability
Balance at January 1, 2011	$	8,172
Issuance of additional warrants		4,994
Exercise of warrants		(4,842	)
Change in fair value of warrant liability		4,763
Balance at December 31, 2011	$	13,087
Issuance of additional warrants		11,077
Exercise of warrants		(17	)
Warrants reclassified to equity due to change in term		(15,048	)
Change in fair value of warrant liability		(8,725	)
Balance at December 31, 2012	$	374

Reconciliation of derivative liability measured at fair value on a recurring basis

	Derivative Liability
Balance at January 1, 2011	$	2,120
Issuance of additional preferred stock and other		252
Conversion of preferred stock		(7,290	)
Change in fair value of derivative liability		5,452
Balance at December 31, 2011		534
Issuance of additional preferred stock and other		793
Conversion of preferred stock		(1,350	)
Change in fair value of derivative liability		23
Balance at December 31, 2012	$	—