Summary Of Significant Accounting Policies (Other Income - Net) (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Interest income					$ (2,710)	$ (2,162)	$ (1,823)
Interest on regulatory deferrals					(990)	(1,288)	(1,308)
Equity-related AFUDC					(6,554)	(6,669)	(8,475)
Non-service portion of pension and other postretirement benefit expenses	$ 2,000	$ 1,900	$ 1,800	$ 2,000	5,156	7,670	10,058
Net loss on investments					5,369	4,160	2,152
Other expense (income)					1,187	(1,104)	(624)
Other income-net					$ 1,458	$ 607	$ (20)