| **Segment Information (Company's Segment Information, Continuing Operations) (Details) - USD ($) $ in Thousands** | 3 Months Ended |
|-------------------------------------------------------------------------------------------------------------------|----------------|
||
| **Segment Reporting Information [Line Items]**                                                                    |           |   |
| Operating revenues                                                                                                | $ 255,585      | $ 201,132 |
| Operations and maintenance expense                                                                                | 106,637        | 79,314 |
| Purchased gas                                                                                                     | 12,770         |   |
| Depreciation and amortization                                                                                     | 46,245         | 39,410 |
| Total taxes other than income                                                                                     | 16,436         | 14,969 |
| Operating income (loss)                                                                                           | 73,497         | 67,439 |
| Interest expense, net                                                                                             | 30,087         | 27,850 |
| Interest income                                                                                                   | 5,035          | 19 |
| Allowance for funds used during construction                                                                      | 2,948          | 4,056 |
| Change in fair value of interest rate swap agreements                                                             |           | 34,782 |
| Equity earnings in joint venture                                                                                  | (127)          | 543 |
| Provision for income taxes                                                                                        | (7,124)        | (8,170) |
| Net income (loss)                                                                                                 | 51,781         | 16,924 |
| Capital expenditures                                                                                              | 118,734        | 133,792 |
| Water [Member] | Regulated [Member]                                                                               |           |   |
| **Segment Reporting Information [Line Items]**                                                                    |           |   |
| Operating revenues                                                                                                | 216,197        | 200,220 |
| Operations and maintenance expense                                                                                | 73,694         | 74,338 |
| Depreciation and amortization                                                                                     | 41,511         | 39,261 |
| Operating income (loss)                                                                                           | 86,506         | 72,865 |
| Interest expense, net                                                                                             | 25,495         | 23,658 |
| Allowance for funds used during construction                                                                      | 2,912          | 4,056 |
| Provision for income taxes                                                                                        | 3,127          | 936 |
| Net income (loss)                                                                                                 | 59,934         | 52,169 |
| Capital expenditures                                                                                              | 110,606        | 133,792 |
| Natural Gas [Member] | Regulated [Member]                                                                         |           |   |
| **Segment Reporting Information [Line Items]**                                                                    |           |   |
| Operating revenues                                                                                                | 38,544         |   |
| Operations and maintenance expense                                                                                | 8,823          |   |
| Purchased gas                                                                                                     | 12,770         |   |
| Depreciation and amortization                                                                                     | 4,569          |   |
| Operating income (loss)                                                                                           | 11,715         |   |
| Interest expense, net                                                                                             | 1,887          |   |
| Allowance for funds used during construction                                                                      | 36             |   |
| Provision for income taxes                                                                                        | (3,448)        |   |
| Net income (loss)                                                                                                 | 13,398         |   |
| Capital expenditures                                                                                              | 8,128          |   |
| Other [Member]                                                                                                    |           |   |
| **Segment Reporting Information [Line Items]**                                                                    |           |   |
| Operating revenues                                                                                                | 844            | 912 |
| Operations and maintenance expense                                                                                | 24,120         | 4,976 |
| Purchased gas                                                                                                     |                |  |
| Depreciation and amortization                                                                                     | 165            | 149 |
| Operating income (loss)                                                                                           | (24,724)       | (5,426) |
| Interest expense, net                                                                                             | 2,705          | 4,192 |
| Allowance for funds used during construction                                                                      |                |  |
| Change in fair value of interest rate swap agreements                                                             |                | 34,782 |
| Equity earnings in joint venture                                                                                  | (127)          | 543 |
| Provision for income taxes                                                                                        | (6,803)        | (9,106) |
| Net income (loss)                                                                                                 | (21,551)       | (35,245) |
| Capital expenditures                                                                                              |                |  |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
In a business combination achieved in stages, this element represents the amount of net gain (loss) recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of income (loss) for proportionate share of equity method investee's income (loss).
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of operating interest income, including, but not limited to, amortization and accretion of premiums and discounts on securities.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.
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| - Definition
The net result for the period of deducting operating expenses from operating revenues.
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No definition available.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash outflow for acquisition of buildings (properties) whether for investment or use.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Total increase in earnings in the period representing the cost of equity (based on assumed rate of return) and/or borrowed funds (based on interest rate) used to finance construction of regulated assets, which is expected to be recovered through rate adjustments.
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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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| - 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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No definition available.
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| - Definition
Amount of operating expense for purchased gas and petroleum of regulated operation.
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| - Definition
Amount of operating expense for routine plant maintenance, repairs and operations of regulated operation.
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| - Definition
Amount of operating expense for taxes other than income taxes of regulated operation.
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| - Definition
Interest expense, net of AFUDC which represents capitalized costs used to finance the construction of utility plants.
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No definition available.
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