Fair Value (Reconciliation For All Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) - Level 3 [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ (2,716)	$ (12,968)	$ (5,262)	$ (16,409)
Included in regulatory assets/liabilities	625	1,829	8,584	155
Settlements	(901)	1,314	(6,314)	6,429
Ending Balance	(2,992)	(9,825)	(2,992)	(9,825)
Natural Gas Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(2,104)	(2,805)	(2,774)	(3,164)
Included in regulatory assets/liabilities	(829)	(768)	8,148	(565)
Settlements	(59)	93	(8,366)	249
Ending Balance	(2,992)	(3,480)	(2,992)	(3,480)
Power Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(612)	(10,163)	(2,488)	(13,245)
Included in regulatory assets/liabilities	1,454	2,597	436	720
Settlements	(842)	1,221	2,052	6,180
Ending Balance	$ 0	$ (6,345)	$ 0	$ (6,345)