Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Allowance for losses and nondeductible accruals	$ 53,967	$ 56,479
Net operating loss carryforward	190,603	140,863
Alternative minimum tax and research and development tax credit carryforward	5,409	5,409
Deferred tax assets, total	249,979	202,751
Depreciation, depletion, amortization, and impairment	(440,690)	(464,295)
Net deferred tax liability	(190,711)	(261,544)
Current deferred tax asset	25,211	14,206
Non-current-deferred tax liability	$ (215,922)	$ (275,750)