Interest Expense (Interest Expense Schedule) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Contractual interest on Convertible Debentures	$ 10,156	$ 10,156	$ 20,312	$ 20,312
Contractual interest on Notes	15,234	15,234	30,469	24,271
Amortization of debt discount on the Convertible Debentures	2,744	2,527	5,433	5,004
Credit facility and other interest expense	725	586	1,449	933
Total interest expense	$ 28,859	$ 28,503	$ 57,663	$ 50,520