Income Taxes (Schedule Of Significant Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Abstract]
Receivables allowance	$ 456	$ 1,132
Inventory	177	42
Asset retirement obligation	492	443
Accrued liabilities	8,695	9,148
Operating loss carryforward	32,946	5,472
Goodwill and intangibles	8,298	10,399
Deferred compensation	6,732	5,770
Total deferred tax assets	57,796	32,406
Property and equipment	199,795	145,410
Prepaid expenses	2,398	2,099
Total deferred tax liabilities	202,193	147,509
Deferred tax assets-current	39,154	8,290
Deferred tax liabilities - non-current	183,551	123,393
Net deferred tax liability	$ (144,397)	$ (115,103)