Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred income tax assets
Net operating loss carryforward - Federal and State	$ 53,648	$ 42,442
Property and equipment	20,425	55,307
Stock-based compensation	4,245	4,469
Allowance for doubtful accounts	476	806
Fair value of derivative instruments	0	75
Valuation allowance	(1,188)	(681)
Other	1,755	1,335
Deferred income tax assets	79,361	103,753
Deferred income tax liabilities
Unamortized discount on 4.375% Convertible Senior Notes	(382)	(1,329)
Capitalized interest	(55,410)	(45,469)
Fair value of derivative instruments	(10,222)	(13,123)
Deferred income tax liabilities	(66,014)	(59,921)
Net deferred income tax asset	$ 13,347	$ 43,832