Business Segment Information (Schedule Of Reconciliation Of Operating Profit (Loss) From Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Business Segment Information [Abstract]
Segment profits	$ 116,732	$ 103,211	$ 221,301	$ 196,514
General and administrative expenses	(42,953)	(49,321)	(82,512)	(91,278)
Depreciation and amortization	(51,785)	(52,067)	(103,490)	(101,848)
Loss on disposal of assets	(916)	(790)	(237)	(1,879)
Operating income	$ 21,078	$ 1,033	$ 35,062	$ 1,509