Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Allowance for losses and nondeductible accruals	$ 74,890	$ 53,376
Net operating loss carryforward	56,020	47,683
Alternative minimum tax credit carryforward	1,972	0
Deferred tax assets, total	132,882	101,059
Depreciation, depletion, amortization and impairment	(819,893)	(773,246)
Net deferred tax liability	(687,011)	(672,187)
Current deferred tax asset	(8,765)	(10,936)
Non-current-deferred tax liability	$ 695,776	$ 683,123