Business Segment Information (Schedule Of Reconciliation Of Operating Profit (Loss) From Segments) (Details) - USD ($) $ in Thousands	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Segment Information [Abstract]
Segment profits	$ 24,992	$ 34,317	$ 37,022	$ 66,412	$ 128,729	$ 129,835	$ 116,732	$ 104,569		$ 162,743	$ 479,865	$ 394,816
General and administrative										(143,458)	(167,301)	(171,439)
Depreciation and amortization										(241,471)	(217,480)	(209,747)
Loss on disposal of assets										(1,602)	(1,974)	(2,873)
Goodwill Impairment		$ (81,900)			$ (34,700)				$ (81,900)	(81,877)	(34,703)
Operating (loss) income										$ (305,665)	$ 58,407	$ 10,757