Business Segment Information (Schedule Of Reconciliation Of Operating Profit (Loss) From Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Business Segment Information [Abstract]
Segment profits	$ 102,054	$ 118,009	$ 298,568	$ 380,082
General and administrative expenses	(43,179)	(43,742)	(134,457)	(133,213)
Depreciation and amortization	(53,623)	(48,272)	(155,471)	(137,792)
Loss on disposal of assets	(411)	(424)	(2,290)	(3,123)
Operating income	$ 4,841	$ 25,571	$ 6,350	$ 105,954