Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Computed expected tax benefit	$ (62,008)	$ (17,513)	$ (98,785)
State and foreign income taxes	12,604	10,970	10,437
Reduction in value of assets		(233)	27,680
U.S. Tax Reform	32,890	21,353
Other	2,586	(19,203)	17,665
Income tax benefit	$ (13,928)	$ (4,626)	$ (43,003)