Other Comprehensive Income (Loss) (Schedule Of Changes In AOCI Balances By Component (After-Tax)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	$ 1,553,023
Total other comprehensive income, net of tax	193	$ 1,150
Balance at the end of the period	1,560,127
Defined Benefit Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(40,865)	(38,242)
Amounts reclassified from AOCI	268	247
Total other comprehensive income, net of tax	268	247
Balance at the end of the period	(40,597)	(37,995)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(4,864)	(4,603)
Other comprehensive gain (loss) before reclassifications	(54)	930
Total other comprehensive income, net of tax	(54)	930
Balance at the end of the period	(4,918)	(3,673)
Unrealized Gain (Loss) in Fair Value of Investments, net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	316	656
Other comprehensive gain (loss) before reclassifications	(21)	8
Total other comprehensive income, net of tax	(21)	8
Balance at the end of the period	295	664
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		24
Other comprehensive gain (loss) before reclassifications		(35)
Total other comprehensive income, net of tax		(35)
Balance at the end of the period		(11)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(45,413)	(42,165)
Other comprehensive gain (loss) before reclassifications	(75)	903
Amounts reclassified from AOCI	268	247
Total other comprehensive income, net of tax	193	1,150
Balance at the end of the period	$ (45,220)	$ (41,015)