Convertible Senior Notes (Interest Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Debt Instrument [Line Items]
Amortization of debt issuance costs			$ 1,163	$ 646
Amortization of debt discount			10,273	5,216
Senior Notes [Member] | Convertible Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Contractual interest expense	$ 2,482	$ 0	4,634	0
Amortization of debt issuance costs	233	0	436	0
Amortization of debt discount	2,538	0	4,739	0
Total	$ 5,253	$ 0	$ 9,809	$ 0
Effective interest rate of the liability component	6.50%	0.00%	6.50%	0.00%
Senior Notes [Member] | Convertible Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Contractual interest expense	$ 945	$ 945	$ 1,891	$ 1,890
Amortization of debt issuance costs	367	326	728	646
Amortization of debt discount	2,781	2,621	5,534	5,216
Total	$ 4,093	$ 3,892	$ 8,153	$ 7,752
Effective interest rate of the liability component	6.02%	6.02%	6.02%	6.02%