Fair Value (Reconciliation For All Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ (21,576)	$ (25,586)	$ (27,124)	$ (23,758)
Included in regulatory assets/liabilities	(2,052)	(2,735)	(3,361)	(9,672)
Settlements	0	282	6,857	5,391
Ending Balance	(23,628)	(28,039)	(23,628)	(28,039)
Natural Gas Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(6,857)	(6,825)	(5,039)	(35)
Included in regulatory assets/liabilities	336	1,800	(2,960)	(5,586)
Settlements	0	282	1,478	878
Ending Balance	(6,521)	(4,743)	(6,521)	(4,743)
Power Option Agreement [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(105)	(145)	(124)	(424)
Included in regulatory assets/liabilities	(692)	28	(673)	307
Settlements	0	0	0	0
Ending Balance	(797)	(117)	(797)	(117)
Power Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(14,614)	(18,616)	(21,961)	(23,299)
Included in regulatory assets/liabilities	(1,696)	(4,563)	272	(4,393)
Settlements	0	0	5,379	4,513
Ending Balance	$ (16,310)	$ (23,179)	$ (16,310)	$ (23,179)