Term Loan (Details) (USD $)	3 Months Ended		1 Months Ended	3 Months Ended
	Mar. 31, 2013 MidCap	Mar. 31, 2012 MidCap	Mar. 31, 2012 Term Loan	Mar. 31, 2013 Term Loan	Mar. 31, 2013 Term Loan Minimum
Term Loan
Basis of interest rate				LIBOR
Interest rate margin (as a percent)				6.25%
Fixed annual interest rate (as a percent)					9.50%
Upfront fee due upon repayment of the Term Loan in full			$ 25,000
Additional Final Payment Fee due upon repayment of the Term Loan in full			37,500
Rate of prepayment premium in year three (as a percent)				1.00%
Rate of prepayment premium in year four (as a percent)				0.00%
Original Payment Fee payable upon repayment of term loan in full				500,000
Interest expense on the term loan	$ 300,000	$ 400,000