Summary of Significant Accounting Policies (Schedule Of Items Reclassified Out Of AOCI And The Corresponding Location And Impact On The Condensed Consolidated Statement Of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax benefit (expense)									$ 53,293	$ 28,547	$ 79,502
NET INCOME	$ 30,260	$ 28,801	$ 21,361	$ 15,400	$ 8,712	$ 19,677	$ 11,777	$ 5,126	95,822	$ 45,292	$ 107,936
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Defined benefit pension plan adjustments									1,745
Income tax benefit (expense)									(646)
NET INCOME									$ 1,099