Convertible Senior Notes (Interest Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Debt Instrument [Line Items]
Amortization of debt issuance costs			$ 1,793	$ 985
Amortization of debt discount			15,739	7,889
Senior Notes [Member] | Convertible Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Contractual interest expense	$ 2,505	$ 0	7,139	0
Amortization of debt issuance costs	248	0	684	0
Amortization of debt discount	2,630	0	7,369	0
Total	$ 5,383	$ 0	$ 15,192	$ 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	$ 2,836	$ 2,836
Amortization of debt issuance costs	382	340	1,110	985
Amortization of debt discount	2,836	2,673	8,370	7,889
Total	$ 4,163	$ 3,958	$ 12,316	$ 11,710
Effective interest rate of the liability component	6.02%	6.02%	6.02%	6.02%