Summary Of Significant Accounting Policies (Schedule Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ (1,545,010)	$ (1,638,943)
Net other comprehensive (income) loss	3,665	523
Ending Balance	(1,622,590)	(1,675,528)
(Gain) Loss On Investments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(557)	(656)
Change excluding amounts reclassified from accumulated other comprehensive loss	$ (18)	$ (79)
Amounts reclassified from accumulated other comprehensive loss
Net other comprehensive (income) loss	$ (18)	$ (79)
Ending Balance	(575)	(735)
(Gain) Loss On Cash Flow Hedges [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(8,160)	(3,416)
Change excluding amounts reclassified from accumulated other comprehensive loss	4,431	1,350
Amounts reclassified from accumulated other comprehensive loss	(371)	(388)
Net other comprehensive (income) loss	4,060	962
Ending Balance	(4,100)	(2,454)
Defined Benefit Pension Plan [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	16,361	16,508
Amounts reclassified from accumulated other comprehensive loss	(377)	(360)
Net other comprehensive (income) loss	(377)	(360)
Ending Balance	15,984	16,148
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	7,644	12,436
Change excluding amounts reclassified from accumulated other comprehensive loss	4,413	1,271
Amounts reclassified from accumulated other comprehensive loss	(748)	(748)
Net other comprehensive (income) loss	3,665	523
Ending Balance	$ 11,309	$ 12,959