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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ (25,586)	$ (10,707)	$ (23,758)	$ (16,435)
Included in regulatory assets/liabilities	(2,735)	(3,980)	(9,672)	5,329
Settlements	(282)	0	(5,391)	(3,581)
Ending Balance	(28,039)	(14,687)	(28,039)	(14,687)
Natural Gas Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(6,825)	(2,183)	(35)	(1,219)
Included in regulatory assets/liabilities	1,800	712	(5,586)	2,796
Settlements	(282)	0	(878)	(3,048)
Ending Balance	(4,743)	(1,471)	(4,743)	(1,471)
Power Option Agreement [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(145)	(605)	(424)	(775)
Included in regulatory assets/liabilities	28	243	307	413
Settlements	0	0	0	0
Ending Balance	(117)	(362)	(117)	(362)
Power Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(18,616)	(7,919)	(23,299)	(14,441)
Included in regulatory assets/liabilities	(4,563)	(4,935)	(4,393)	2,120
Settlements	0	0	(4,513)	(533)
Ending Balance	$ (23,179)	$ (12,854)	$ (23,179)	$ (12,854)