Income Taxes (Schedule Of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowance for doubtful accounts	$ 1,291	$ 856
Operating loss and tax credit carryforwards	136,647	146,926
Compensation and employee benefits	35,532	38,006
Decommissioning liabilities	29,405	27,979
Operating leases	1,002
Other	24,903	25,331
Deferred tax assets, gross	228,780	239,098
Valuation allowance	(84,741)	(25,571)
Net deferred tax assets	144,039	213,527
Deferred tax liabilities:
Property, plant and equipment	114,024	146,971
Notes receivable	12,977	12,977
Goodwill and other intangible assets	20,285	38,955
Other		14,624
Deferred tax liabilities	147,286	$ 213,527
Net deferred tax liability	$ 3,247