Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Computed expected tax benefit	$ (17,513)	$ (98,785)	$ (109,157)
State and foreign income taxes	4,019	10,437	16,437
Reduction in value of assets	(233)	27,680
U.S. Tax Reform			(39,603)
Other	9,101	17,665	761
Income tax benefit	$ (4,626)	$ (43,003)	$ (131,562)