Other Comprehensive Income (Loss) (Schedule Of Changes In AOCI Balances By Component (After-Tax)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period			$ 1,420,227
Net other comprehensive income (loss)	$ (76)	$ (1,160)	1,074	$ (1,713)
Balance at the end of the period	1,492,833		1,492,833
Defined Benefit Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(37,995)	(40,268)	(38,242)	(40,268)
Amounts reclassified from AOCI	324		571
Net other comprehensive income (loss)	324		571
Balance at the end of the period	(37,671)	(40,268)	(37,671)	(40,268)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(3,673)	(1,977)	(4,603)	(1,389)
Other comprehensive income (loss) before reclassifications	(258)		672
Net other comprehensive income (loss)	(258)	(1,146)	672	(1,734)
Balance at the end of the period	(3,931)	(3,123)	(3,931)	(3,123)
Unrealized Gain (Loss) in Fair Value of Investments, net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	664	(120)	656	(110)
Other comprehensive income (loss) before reclassifications	(153)		(145)
Net other comprehensive income (loss)	(153)	(74)	(145)	(84)
Balance at the end of the period	511	(194)	511	(194)
Unrealized Gain (Loss) in Fair Value of Interest Rate Swap, net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(11)	194	24	149
Other comprehensive income (loss) before reclassifications	11		(24)
Net other comprehensive income (loss)	11	60	(24)	105
Balance at the end of the period		254		254
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(41,015)	(42,171)	(42,165)	(41,618)
Other comprehensive income (loss) before reclassifications	(400)		503
Amounts reclassified from AOCI	324		571
Net other comprehensive income (loss)	(76)	(1,160)	1,074	(1,713)
Balance at the end of the period	$ (41,091)	$ (43,331)	$ (41,091)	$ (43,331)