Subsequent Events (Details) (Subsequent events, USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended
	Jul. 17, 2013
Subsequent event
Shares of common stock sold in underwritten public offering	5,750,000
Public offering price (in dollars per share)	$ 5.00
Net proceeds from sale of common stock and convertible senior notes	$ 147.4
Convertible senior notes
Subsequent event
Convertible senior notes issued	125.0
Interest rate (as a percent)	4.50%
Loan and security agreement
Subsequent event
Extension period for interest-only payments	6 months
Loan and security agreement | Minimum
Subsequent event
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