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
	Mar. 31, 2019	Mar. 31, 2018
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ (5,262)	$ (16,409)
Included in regulatory assets/liabilities	7,959	(1,674)
Settlements	(5,413)	5,115
Ending Balance	(2,716)	(12,968)
Natural Gas Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(2,774)	(3,164)
Included in regulatory assets/liabilities	8,977	203
Settlements	(8,307)	156
Ending Balance	(2,104)	(2,805)
Power Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(2,488)	(13,245)
Included in regulatory assets/liabilities	(1,018)	(1,877)
Settlements	2,894	4,959
Ending Balance	$ (612)	$ (10,163)