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	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ (27,124)	$ (23,758)	$ (16,435)	$ (22,551)
Included in regulatory assets/liabilities	(11,906)	(5,778)	4,020
Settlements	8,540	(1,545)	2,096
Natural Gas Exchange Agreements [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	(5,039)	(35)	(1,219)	(2,379)
Included in regulatory assets/liabilities	(6,008)	3,873	2,298
Settlements	1,004	(2,689)	(1,138)
Power Exchange Agreements [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	(21,961)	(23,299)	(14,441)	(18,692)
Included in regulatory assets/liabilities	(6,198)	(10,002)	1,017
Settlements	7,536	1,144	3,234
Power Option Agreement [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	(124)	(424)	(775)	$ (1,480)
Included in regulatory assets/liabilities	300	351	705
Settlements	$ 0	$ 0	$ 0