Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Abstract]
Depreciation and depletion	$ 396,355	$ 384,313
OID on Convertible Notes	37,067	34,169
Equity investments in production facilities	76,911	69,495
Prepaid and other	14,779	15,616
Total deferred tax liabilities	525,112	503,593
Net operating loss carryforward	(34,987)	(38,718)
Asset retirement obligations	(88,279)	(81,345)
Reserves, accrued liabilities and other	(39,995)	(27,588)
Total deferred tax assets	(163,261)	(147,651)
Valuation allowance	14,310	8,497
Current deferred tax asset	(41,449)	(49,200)
Noncurrent deferred tax liabilities	417,610	413,639
Net deferred tax liability	$ 376,161	$ 364,439