Debt - Term Debt Narrative (Details) (USD $)	0 Months Ended				0 Months Ended	1 Months Ended		0 Months Ended		12 Months Ended
	Jul. 27, 2012	Jul. 18, 2011	Dec. 31, 2012	Dec. 31, 2009	Jul. 30, 2012 Oxford/SVB [Member]	Jun. 30, 2011 Oxford/SVB [Member]	Dec. 31, 2011 Oxford/SVB [Member]	Jul. 30, 2012 Oxford/SVB [Member] Revolving Credit Facility [Member]	Jun. 30, 2008 Oxford/SVB [Member] Loan And Security Agreement [Member]	Dec. 31, 2012 Minimum [Member] Oxford/SVB [Member]	Dec. 31, 2012 Maximum [Member] Oxford/SVB [Member]
Debt Instrument [Line Items]
Debt instrument, outstanding									$ 18,000,000
Warrant exercisable to Healthcare Royalty, shares		225,000				26,455
Warrants exercise price (in usd per share)	$ 2.50					$ 3.78
Term of common stock warrant exercisable	5 years	10 years				7 years
Debt discount							76,000
Fair value of warrant liabilities			9,308,000
Long term debt under loan and security agreement			30,000,000			25,000,000	25,000,000
Revolving credit facility				200,000		10,000,000
Interest rate						12.06%
Revolving credit facility, interest rate description						equal to the greater of 3.29% above SVB's prime rate or 7.29%
Revolving credit facility, interest rate										3.29%	7.29%
Percentage paid for unused portion of revolving credit facility						0.50%
Amount outstanding under revolving credit facility							5,151,000
Principal and interest repaid					19,492,000
Final payment to terminate debt					1,200,000
Prepayment premium to terminate debt					$ 400,000			$ 100,000
Percentage of principal as perpayment premium					2.00%