| **Summary Of Significant Accounting Policies (Schedule Of Disaggregation Of Revenue) (Details) - USD ($) $ in Thousands** | 3 Months Ended | 12 Months Ended |
|---------------------------------------------------------------------------------------------------------------------------|----------------|-----------------|
||
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenue                                                                                                                   | $ 226,042      | $ 243,626       | $ 218,892 | $ 201,132 | $ 205,747 | $ 226,137 | $ 211,860 | $ 194,347 | $ 889,692 | $ 838,091 | $ 809,525 |
| Water [Member]                                                                                                            |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 767,400 | 731,441 |   |
| Revenue                                                                                                                   |           |            |   |   |   |   |   |   | 767,480 | 730,733 |   |
| Wastewater [Member]                                                                                                       |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 105,204 | 94,170 |   |
| Revenue                                                                                                                   |           |            |   |   |   |   |   |   | 105,115 | 94,478 |   |
| Other [Member]                                                                                                            |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 13,835 | 9,427 |   |
| Revenue                                                                                                                   |           |            |   |   |   |   |   |   | 17,097 | 12,880 |   |
| Other [Member] | Other And Eliminations [Member]                                                                          |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenue                                                                                                                   |           |            |   |   |   |   |   |   | 3,262 | 3,453 |   |
| Residential [Member] | Water [Member]                                                                                     |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 518,192 | 482,946 |   |
| Residential [Member] | Wastewater [Member]                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 83,561 | 73,418 |   |
| Commercial [Member] | Water [Member]                                                                                      |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 145,599 | 133,753 |   |
| Commercial [Member] | Wastewater [Member]                                                                                 |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 15,222 | 13,147 |   |
| Fire Protection [Member] | Water [Member]                                                                                 |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 33,589 | 32,236 |   |
| Industrial [Member] | Water [Member]                                                                                      |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 30,667 | 28,848 |   |
| Industrial [Member] | Wastewater [Member]                                                                                 |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 1,765 | 1,857 |   |
| Other Water [Member] | Water [Member]                                                                                     |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 39,353 | 53,658 |   |
| Other Wastewater [Member] | Wastewater [Member]                                                                           |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | 4,656 | 5,748 |   |
| Alternative Revenue Program [Member] | Water [Member]                                                                     |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenue                                                                                                                   |           |            |   |   |   |   |   |   | 80 | (708) |   |
| Alternative Revenue Program [Member] | Wastewater [Member]                                                                |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenue                                                                                                                   |           |            |   |   |   |   |   |   | (89) | 308 |   |
| Other Utility [Member] | Other [Member]                                                                                   |           |            |   |   |   |   |   |   |   |   |   |
| **Disaggregation of Revenue [Line Items]**                                                                                |           |            |   |   |   |   |   |   |   |   |   |
| Revenues from contracts with customers                                                                                    |           |            |   |   |   |   |   |   | $ 13,835 | $ 9,427 |   |

| 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.
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| - Definition
Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).
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