Summary Of Significant Accounting Policies (Reclassifications Out of Accumulated Other Comprehensive Loss) (Details) - Reclassification Out of Accumulated Other Comprehensive Income [Member] - Accumulated Defined Benefit Plans Adjustment [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net prior service cost	$ (228)	$ (299)
Amortization of net loss	2,995	3,638
Adjustment due to effects of regulation	(2,508)	(3,058)
Total before tax	259	281
Tax benefit (expense)	(55)	(98)
Net of tax	$ 204	$ 183