Accounting For Income Taxes (Schedule Of Recovery Of Deferred Income Tax Liabilities) (Details) (Imported) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Excess Deferred Income Taxes Plant Related [Member] [Member]
Schedule of Income Tax Related Regulatory Assets and Liabilities [Line Items]
Regulatory Liabilities	$ 436,700	$ 442,300
Excess Deferred Income Taxes Non-plant Related [Member]
Schedule of Income Tax Related Regulatory Assets and Liabilities [Line Items]
Regulatory Liabilities	18,500
Deferred Income Tax Charge [Member]
Schedule of Income Tax Related Regulatory Assets and Liabilities [Line Items]
Regulatory Liabilities	453,610	460,542
Deferred Income Tax Charge [Member]
Schedule of Income Tax Related Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	$ 91,188	$ 90,315