| **Acquisitions (Details)**                                           |                 | 1 Months Ended | 3 Months Ended | 12 Months Ended |              |               |
|----------------------------------------------------------------------|-----------------|----------------|----------------|-----------------|--------------|---------------|
||
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Goodwill                                                             |            | $ 52,726,000   |           |            |         | $ 52,726,000  |   |   |   | $ 42,230,000 |   |   |   | $ 52,726,000 | $ 42,230,000 | $ 42,208,000 |   |   |
| Net income                                                           |            |           |           |            |         | (3,657,000)   | $ 78,216,000 | $ 66,590,000 | $ 50,839,000 | 53,473,000 | $ 76,225,000 | $ 60,968,000 | $ 49,072,000 | 191,988,000 | 239,738,000 | 234,182,000 |   |   |
| Operating revenues                                                   |            |           |           |            |         | 205,747,000   | $ 226,137,000 | $ 211,860,000 | $ 194,347,000 | 203,312,000 | $ 215,008,000 | $ 203,418,000 | $ 187,787,000 | 838,091,000 | $ 809,525,000 | 819,875,000 |   |   |
| Bridge commitment                                                    | $ 5,100,000,000 |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Commitments terminated                                               |            |           |           |            |         | 1,633,000,000 |   |   |   |   |   |   |   |   |   |   |   |   |
| 2016 Acquisition [Member]                                            |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of acquisitions completed | item                              |            |           |           |            |         |          |   |   |   |   |   |   |   |   | 18 |   |   |   |
| Number of customers | customer                                       |            |           |           |            |         |          |   |   |   |   |   |   |   |   | 2,469 |   |   |   |
| Cash paid for acquisitions                                           |            |           |           |            |         |          |   |   |   |   |   |   |   |   | $ 5,518,000 |   |   |   |
| Operating revenues included in the consolidated financial statements |            |           |           |            |         |          |   |   |   |   |   |   |   | 4,966,000 | $ 4,896,000 | $ 3,809,000 |   |   |
| 2017 Acquisition [Member]                                            |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of acquisitions completed | item                              |            |           |           |            |         |          |   |   |   |   |   |   |   |   | 4 |   |   |   |
| Number of customers | customer                                       |            |           |           |            |         |          |   |   |   |   |   |   |   |   | 1,003 |   |   |   |
| Cash paid for acquisitions                                           |            |           |           |            |         |          |   |   |   |   |   |   |   |   | $ 5,860,000 |   |   |   |
| Number of states | state                                             |            |           |           |            |         |          |   |   |   |   |   |   |   |   | 2 |   |   |   |
| Goodwill                                                             |            |           |           |            |         |          |   |   |   | $ 72,000 |   |   |   |   | $ 72,000 |   |   |   |
| Operating revenues included in the consolidated financial statements |            |           |           |            |         |          |   |   |   |   |   |   |   | $ 846,000 | $ 461,000 |   |   |   |
| Superior Water Company, Inc. [Member]                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of customers | customer                                       |            |           |           |            | 4,108        |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Cash paid for acquisitions                                           |            |           |           |            | $ 3,905,000  |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Total purchase price                                                 |            |           |           |            | $ 16,750,000 |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Shares issued | shares                                               |            |           |           |            | 439,943      |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Acquired property, plant and equipment                               |            |           |           |            | $ 25,167,000 |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Contributions in aid of construction                                 |            |           |           |            | 16,565,000   |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Goodwill                                                             |            |           |           |            | $ 8,622,000  |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Water And Wastewater Utility Systems [Member]                        |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of municipalities | item                                      |            |           |           | 4               |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of customers | customer                                       |            |           |           | 4,000           |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Total purchase price                                                 |            |           |           | $ 38,950,000    |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of states | state                                             |            |           |           | 2               |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Wastewater Utility System [Member]                                   |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of acquisitions completed | item                              |            |           |           |            |         |          |   |   |   |   |   |   |   | 7 |   |   |   |   |
| Number of customers | customer                                       |            |           |           |            |         |          |   |   |   |   |   |   |   | 8,661 |   |   |   |   |
| Total purchase price                                                 |            | 42,519,000     |           |            |         | 42,519,000    |   |   |   |   |   |   |   | $ 42,519,000 |   |   |   |   |
| Operating revenues                                                   |            |           |           |            |         |          |   |   |   |   |   |   |   | 3,308,000 |   |   |   |   |
| Interest Rate Swap [Member]                                          |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Interest rate swap                                                   |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   | $ 850,000 | $ 850,000 |
| Pennsylvania [Member] | LDC Funding LLC [Member]                     |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of acquisitions completed | item                              | 5               |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of customers | customer                                       | 740,000         |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Total purchase price                                                 | $ 4,275,000,000 |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Contingent consideration                                             | 120,000,000     |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Assumed liabilities including debt                                   | 1,300,000,000   |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Decrease in purchase price                                           | $ 1,300,000,000 |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Pennsylvania [Member] | Wastewater Utility System [Member]           |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Total purchase price                                                 |            | $ 28,300,000   |           |            |         | $ 28,300,000  |   |   |   |   |   |   |   | $ 28,300,000 |   |   |   |   |
| Number of waste water systems | item                                 |            | 49,000         |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Limerick [Member] | Wastewater Utility System [Member]               |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of customers | customer                                       |            |           |           | 5,497           |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Total purchase price                                                 |            |           |           | $ 74,836,000    |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Acquired property, plant and equipment                               |            |           |           | 64,759,000      |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Goodwill                                                             |            |           |           | $ 10,790,000    |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Norriton Township [Member] | Wastewater Utility System [Member]      |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of customers | customer                                       |            |           | 4,950          |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Total purchase price                                                 |            |           | $ 21,000,000   |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Cheltenham Township [Member] | Wastewater Utility System [Member]    |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| **Business Acquisition [Line Items]**                                |            |           |           |            |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of customers | customer                                       |            |           |           | 10,500          |         |          |   |   |   |   |   |   |   |   |   |   |   |   |
| Total purchase price                                                 |            |           |           | $ 50,250,000    |         |          |   |   |   |   |   |   |   |   |   |   |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Short-Term financing which is expected to be paid back relatively quickly, such as by a subsequent longer-term loan. Also called swing loan or bridge financing.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(13)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)(a)(1)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(19)(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
+ Details**Name:**us-gaap_BridgeLoan**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of shares of equity interests issued or issuable to acquire entity.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b)(4) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479
+ Details**Name:**us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued**Namespace Prefix:**us-gaap_**Data Type:**xbrli:sharesItemType**Balance Type:**na**Period Type:**duration |
| 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.
+ Details**Name:**us-gaap_BusinessAcquisitionLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463
+ Details**Name:**us-gaap_BusinessAcquisitionsProFormaRevenue**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of liability recognized arising from contingent consideration in a business combination.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 35 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476
+ Details**Name:**us-gaap_BusinessCombinationContingentConsiderationLiability**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of liabilities assumed at the acquisition date.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472
+ Details**Name:**us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of other assets expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472
+ Details**Name:**us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of property, plant, and equipment recognized as of the acquisition date.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 55 -Paragraph 37 -URI http://asc.fasb.org/extlink&oid=108330185&loc=d3e2207-128464Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472
+ Details**Name:**us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472
+ Details**Name:**us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of the assets less the liabilities of a derivative or group of derivatives.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611
+ Details**Name:**us-gaap_DerivativeFairValueOfDerivativeNet**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Gross amount of debt extinguished.
+ References
No definition available.
+ Details**Name:**us-gaap_ExtinguishmentOfDebtAmount**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266
+ Details**Name:**us-gaap_Goodwill**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669619-108580Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(22)) -URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669625-108580Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(18)) -URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(20)) -URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257
+ Details**Name:**us-gaap_NetIncomeLoss**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The number of businesses acquired by the entity during the period.
+ References
No definition available.
+ Details**Name:**us-gaap_NumberOfBusinessesAcquired**Namespace Prefix:**us-gaap_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585
+ Details**Name:**us-gaap_PaymentsToAcquireBusinessesGross**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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).
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8933-108599Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599
+ Details**Name:**us-gaap_Revenues**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Business Acquisition, Geographical Location, Number Of Municipalities
+ References
No definition available.
+ Details**Name:**wtr_BusinessAcquisitionGeographicalLocationNumberOfMunicipalities**Namespace Prefix:**wtr_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Business Acquisition, Geographical Location, Number Of States
+ References
No definition available.
+ Details**Name:**wtr_BusinessAcquisitionGeographicalLocationNumberOfStates**Namespace Prefix:**wtr_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Business Combination, Increased (Decrease) In Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net
+ References
No definition available.
+ Details**Name:**wtr_BusinessCombinationIncreasedDecreaseInRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet**Namespace Prefix:**wtr_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of customers.
+ References
No definition available.
+ Details**Name:**wtr_NumberOfCustomers**Namespace Prefix:**wtr_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number Of Wastewater Systems
+ References
No definition available.
+ Details**Name:**wtr_NumberOfWastewaterSystems**Namespace Prefix:**wtr_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_BusinessAcquisitionAxis=wtr_TwoThousandSixteenAcquisitionMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_BusinessAcquisitionAxis=wtr_TwoThousandSeventeenAcquisitionMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_BusinessAcquisitionAxis=wtr_SuperiorWaterCompanyInc.Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_BusinessAcquisitionAxis=wtr_WaterAndWastewaterUtilitySystemsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_BusinessAcquisitionAxis=wtr_WastewaterUtilitySystemMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**srt_StatementGeographicalAxis=stpr_PA**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_BusinessAcquisitionAxis=wtr_LdcFundingLlcMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**srt_StatementGeographicalAxis=wtr_LimerickMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**srt_StatementGeographicalAxis=wtr_NorritonTownshipMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**srt_StatementGeographicalAxis=wtr_CheltenhamTownshipMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |