Debt (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended		3 Months Ended
	Feb. 28, 2013	Dec. 31, 2012	Mar. 31, 2013
Loan and Security Agreement
Debt
Period of interest-only payment			12 months
Extension period for interest only payments			6 months
Interest expense			$ 1.1
Discount on loan recorded as a long-term liability to be paid upon full repayment or maturity of the loans			1.2
Outstanding borrowings			38.7
Debt discounts			1.4
Amortization of the debt discounts			0.2
Loan and Security Agreement | Minimum
Debt
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
Loan and Security Agreement | Hercules Technology Growth Capital, Inc.
Debt
Aggregate principal amount of loans received		40.0
Convertible notes | Silver Creek
Debt
Outstanding borrowings			1.6
Debt discounts			0.2
Amortization of the debt discounts			0.1
Aggregate principal amounts	$ 0.3	$ 1.6