Debt (Liability Component and Interest Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Senior Convertible Notes	Aug. 31, 2013 Senior Convertible Notes
Liability Component
Principal amount					$ 150,000
Unamortized debt discount					(37,698)
Net carrying amount	731		731		112,302	111,500
Interest Expense
Contractual interest expense at 1.5% per annum					296
Amortization of debt issuance costs					79
Accretion of debt discount					845
Total	$ 1,272	$ 70	$ 1,376	$ 180	$ 1,220