Summary of Significant Accounting Policies (Schedule Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			$ (1,545,010)	$ (1,638,943)
Net other comprehensive (income) loss	$ 3,324	$ (7,416)	6,989	(6,893)
Ending Balance	(1,669,706)	(1,536,903)	(1,669,706)	(1,536,903)
(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			(98)	(76)
Amounts reclassified from accumulated other comprehensive loss
Net other comprehensive (income) loss			(98)	(76)
Ending Balance	(655)	(732)	(655)	(732)
(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			8,571	(5,388)
Amounts reclassified from accumulated other comprehensive loss			(731)	(709)
Net other comprehensive (income) loss			7,840	(6,097)
Ending Balance	(320)	(9,513)	(320)	(9,513)
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			(753)	(720)
Net other comprehensive (income) loss			(753)	(720)
Ending Balance	15,608	15,788	15,608	15,788
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			8,473	(5,464)
Amounts reclassified from accumulated other comprehensive loss			(1,484)	(1,429)
Net other comprehensive (income) loss			6,989	(6,893)
Ending Balance	$ 14,633	$ 5,543	$ 14,633	$ 5,543