Debt And Interest Expense (Components Of Interest Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Short-term Debt [Line Items]
Contractual interest on Convertible Debentures	$ 0	$ 0	$ 20,015
Interest Expense, Debt	87,063	87,063	87,063
Amortization of debt discount on the Convertible Debentures	0	0	4,236
Other interest expense	3,081	3,548	3,531
Total interest expense	$ 90,144	$ 90,611	$ 114,845