Significant Accounting Policies (Schedule Of Depreciation And Amortization Rates) (Details)	12 Months Ended
	Dec. 31, 2016
Minimum [Member] | Steam Production Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	3.15%
Minimum [Member] | Hydroelectric Production Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	1.06%
Minimum [Member] | Other Production Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	3.15%
Minimum [Member] | Transmission Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	1.58%
Minimum [Member] | Distribution Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	2.16%
Minimum [Member] | General Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	1.57%
Minimum [Member] | Other Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	2.75%
Maximum [Member] | Steam Production Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	3.84%
Maximum [Member] | Hydroelectric Production Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	3.00%
Maximum [Member] | Other Production Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	8.85%
Maximum [Member] | Transmission Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	7.86%
Maximum [Member] | Distribution Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	9.63%
Maximum [Member] | General Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	20.00%
Maximum [Member] | Other Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rates	2.75%