Business Segment Information (Schedule Of Reconciliation Of Operating Profit (Loss) From Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Business Segment Information [Abstract]
Segment profits	$ 138,990	$ 136,647	$ 111,538	$ 89,968	$ 71,807	$ 59,051	$ 53,588	$ 36,933	$ 477,143	$ 221,379	$ 137,039
General and administrative expenses									(142,264)	(107,781)	(104,253)
Depreciation and amortization									(154,341)	(135,001)	(132,520)
Gain (loss) on disposal of assets									(447)	(2,856)	(2,650)
Goodwill impairment											(204,014)
Operating income (loss)									$ 180,091	$ (24,259)	$ (306,398)