Debt (Details) (USD $)			0 Months Ended	12 Months Ended	0 Months Ended					0 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Debt	Nov. 08, 2012 Loan Agreement with Hercules	Dec. 31, 2012 Loan Agreement with Hercules	Nov. 08, 2012 Loan Agreement with Hercules Minimum	Nov. 08, 2012 Loan Agreement with Hercules First alternative interest rate	Nov. 08, 2012 Loan Agreement with Hercules Second alternative interest rate	Dec. 31, 2012 Convertible notes Silver Creek	Dec. 21, 2012 Convertible notes Silver Creek	Dec. 21, 2012 Convertible notes Silver Creek Minimum
Debt
Initial term loan advance			$ 25,000,000
Additional term loan			15,000,000
Minimum stated percentage rate (as a percent)						10.55%
Stated percentage used as basis for calculation of alternative interest rate							10.55%
Description of reference rate that is added to stated percentage rate in calculation of variable rate							prime rate
Percentage points subtracted from alternative interest rate							5.25%
Maximum interest rate on term loan (as a percent)							12.55%
Period of interest-only payment			12 months
Amount of gross proceeds from qualifying equity financing in which holders would automatically convert into the next qualifying equity financing at a 25% dicount										4,000,000
Amount of gross proceeds in one or more transactions prior to December 1, 2013 that the Company may elect to extend the interest-only period by six months					75,000,000
Extension period for interest only payments			6 months
Discount on loan recorded as a long-term liability to be paid upon full repayment or maturity of the loans			1,200,000
Discount on loans related to costs reimbursed by the entity			396,000
Cash interest expense				475,000
Non cash interest expense				78,000
Value of the Company's equity securities available for purchase by the lender			1,000,000
Period to purchase equity securities sold to institutional accredited investors under the Loan Agreement			1 year
Future minimum payments under the loans payable
2013		5,439,000
2014		18,138,000
2015		18,123,000
2016		8,830,000
Loan payable				50,530,000
Less interest				(9,330,000)
Total convertible note outstanding								1,571,000
Less unamortized discount			(1,600,000)	(2,720,000)				(196,000)
Less current portion				(998,000)
Loans payable, net of current portion				37,482,000
Loans payable								1,375,000
Interest rate (as a percent)									6.00%
Discount on automatic conversion into the next qualifying equity financing (as a percent)									25.00%
Derivative liability	$ 196,000								$ 196,000