Interest Expense (Interest Expense Schedule) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Contractual interest on Convertible Debentures	$ 10,156	$ 10,156	$ 20,312	$ 20,312
Amortization of debt discount on the Convertible Debentures	2,527	2,329	5,004	4,611
Credit facility and other interest expense	735	494	1,239	985
Interest capitalized to Property and equipment, net	(149)	(161)	(306)	(377)
Total interest expense	28,503	21,490	50,520	42,875
Due 2023 [Member]
Contractual interest on Notes	8,672	8,672	17,344	17,344
Due 2025 [Member]
Contractual interest on Notes	$ 6,562	$ 0	$ 6,927	$ 0