Interest Expense (Interest Expense Schedule) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Interest Expense [Abstract]
Contractual interest on Convertible Debentures	$ 21,766	$ 21,766	$ 43,532	$ 43,531
Contractual interest on Notes	0	5,067	0	20,015
Amortization of debt discount on the Convertible Debentures	0	1,075	0	4,236
Credit facility and other interest expense	869	884	1,734	1,798
Total interest expense	$ 22,635	$ 28,792	$ 45,266	$ 69,580