Accounting For Income Taxes (Schedule Of Recovery Of Deferred Income Tax Liabilities) (Details) (Imported) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Income Tax Related Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	$ 699,828	$ 579,632
Regulatory Liabilities	396,952	333,883
Deferred Income Tax Charge [Member]
Schedule of Income Tax Related Regulatory Assets and Liabilities [Line Items]
Regulatory Liabilities	28,966	17,609
Deferred Income Tax Charge [Member]
Schedule of Income Tax Related Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	$ 109,853	$ 101,240