| **Employee Stock And Incentive Plan (Summary Of Compensation Costs) (Details) - USD ($) $ in Thousands** | 12 Months Ended |
|----------------------------------------------------------------------------------------------------------|-----------------|
||
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                       |            |   |   |
| Income tax benefit                                                                                       | $ 227           | $ 174 | $ 168 |
| Stock Options [Member]                                                                                   |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                       |            |   |   |
| Income tax benefit                                                                                       | 260             | 193 | 189 |
| Performance Share Units [Member]                                                                         |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                       |            |   |   |
| Stock-based compensation within opertions and maintenance expense                                        | 3,823           | 4,419 | 4,996 |
| Income tax benefit                                                                                       | 1,552           | 1,796 | 2,044 |
| Restricted Stock Units [Member]                                                                          |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                       |            |   |   |
| Stock-based compensation within opertions and maintenance expense                                        | 1,061           | 1,076 | 1,122 |
| Income tax benefit                                                                                       | 438             | 444 | 464 |
| Restricted Stock [Member]                                                                                |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                       |            |   |   |
| Stock-based compensation within opertions and maintenance expense                                        |            |   | 691 |
| Income tax benefit                                                                                       |            |   | $ 287 |
| Stock Awards [Member]                                                                                    |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                       |            |   |   |
| Stock-based compensation within opertions and maintenance expense                                        | 506             | 365 |   |
| Income tax benefit                                                                                       | $ 210           | $ 151 |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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| X                                                                                                                                             |
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| X                                                                                                                                                   |
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