| **Regulatory Assets And Liabilities (Components Of Regulatory Assets And Regulatory Liabilities) (Details) (USD $)In Thousands, unless otherwise specified** | Dec. 31, 2014                                                                                                                          | Dec. 31, 2013                                                                                                                          |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------|
| **Regulatory Of Assets And Liabilities [Line Items]**                                                                                                        |                                                                                                                                   |                                                                                                                                   |
| Regulatory Assets                                                                                                                                            | $ 725,591us-gaap_RegulatoryAssets                                                                                                      | $ 585,140us-gaap_RegulatoryAssets                                                                                                      |
| Regulatory Liabilities                                                                                                                                       | 278,317us-gaap_RegulatoryLiabilities                                                                                                   | 281,014us-gaap_RegulatoryLiabilities                                                                                                   |
| Income Taxes [Member]                                                                                                                                        |                                                                                                                                   |                                                                                                                                   |
| **Regulatory Of Assets And Liabilities [Line Items]**                                                                                                        |                                                                                                                                   |                                                                                                                                   |
| Regulatory Assets                                                                                                                                            | 596,459us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_DeferredIncomeTaxChargesMember                        | 494,308us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_DeferredIncomeTaxChargesMember                        |
| Regulatory Liabilities                                                                                                                                       | 206,940us-gaap_RegulatoryLiabilities/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_DeferredIncomeTaxChargesMember                   | 223,592us-gaap_RegulatoryLiabilities/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_DeferredIncomeTaxChargesMember                   |
| Utility Plant Retirement Costs [Member]                                                                                                                      |                                                                                                                                   |                                                                                                                                   |
| **Regulatory Of Assets And Liabilities [Line Items]**                                                                                                        |                                                                                                                                   |                                                                                                                                   |
| Regulatory Assets                                                                                                                                            | 7,687us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_AssetRetirementObligationCostsMember                    | 12,083us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_AssetRetirementObligationCostsMember                   |
| Regulatory Liabilities                                                                                                                                       | 25,236us-gaap_RegulatoryLiabilities/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_AssetRetirementObligationCostsMember              | 22,365us-gaap_RegulatoryLiabilities/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_AssetRetirementObligationCostsMember              |
| Postretirement Benefits [Member]                                                                                                                             |                                                                                                                                   |                                                                                                                                   |
| **Regulatory Of Assets And Liabilities [Line Items]**                                                                                                        |                                                                                                                                   |                                                                                                                                   |
| Regulatory Assets                                                                                                                                            | 108,586us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_PostretirementBenefitCostsMember                      | 66,534us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_PostretirementBenefitCostsMember                       |
| Regulatory Liabilities                                                                                                                                       | 46,074us-gaap_RegulatoryLiabilities/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_PostretirementBenefitCostsMember                  | 34,983us-gaap_RegulatoryLiabilities/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_PostretirementBenefitCostsMember                  |
| Recoverable Vacation Pay [Member]                                                                                                                            |                                                                                                                                   |                                                                                                                                   |
| **Regulatory Of Assets And Liabilities [Line Items]**                                                                                                        |                                                                                                                                   |                                                                                                                                   |
| Regulatory Assets                                                                                                                                            | 1,605us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= us-gaap_RecoverableVacationPayMember                            |                                                                                                                                   |
| Water Tank Painting [Member]                                                                                                                                 |                                                                                                                                   |                                                                                                                                   |
| **Regulatory Of Assets And Liabilities [Line Items]**                                                                                                        |                                                                                                                                   |                                                                                                                                   |
| Regulatory Assets                                                                                                                                            | 1,533us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= wtr_WaterTankPaintingMember                                     | 2,430us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= wtr_WaterTankPaintingMember                                     |
| Fair Value Adjustment Of Long-Term Debt Assumed In Acquisition [Member]                                                                                      |                                                                                                                                   |                                                                                                                                   |
| **Regulatory Of Assets And Liabilities [Line Items]**                                                                                                        |                                                                                                                                   |                                                                                                                                   |
| Regulatory Assets                                                                                                                                            | 4,004us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= wtr_FairValueAdjustmentOfLongTermDebtAssumedInAcquisitionMember | 4,371us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= wtr_FairValueAdjustmentOfLongTermDebtAssumedInAcquisitionMember |
| Rate Case Filing Expenses And Other [Member]                                                                                                                 |                                                                                                                                   |                                                                                                                                   |
| **Regulatory Of Assets And Liabilities [Line Items]**                                                                                                        |                                                                                                                                   |                                                                                                                                   |
| Regulatory Assets                                                                                                                                            | 5,717us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= wtr_RateCaseFilingExpensesAndOtherMember                        | 5,414us-gaap_RegulatoryAssets/ wtr_RegulatoryAssetsAndLiabilitiesAxis= wtr_RateCaseFilingExpensesAndOtherMember                        |
| Regulatory Liabilities                                                                                                                                       | $ 67us-gaap_RegulatoryLiabilities/ wtr_RegulatoryAssetsAndLiabilitiesAxis= wtr_RateCaseFilingExpensesAndOtherMember                    | $ 74us-gaap_RegulatoryLiabilities/ wtr_RegulatoryAssetsAndLiabilitiesAxis= wtr_RateCaseFilingExpensesAndOtherMember                    |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382
+ Details**Name:**us-gaap_RegulatoryAssets**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394
+ Details**Name:**us-gaap_RegulatoryLiabilities**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**wtr_RegulatoryOfAssetsAndLiabilitiesLineItems**Namespace Prefix:**wtr_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**wtr_RegulatoryAssetsAndLiabilitiesAxis=us-gaap_AssetRetirementObligationCostsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**wtr_RegulatoryAssetsAndLiabilitiesAxis=us-gaap_DeferredIncomeTaxChargesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**wtr_RegulatoryAssetsAndLiabilitiesAxis=us-gaap_PostretirementBenefitCostsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**wtr_RegulatoryAssetsAndLiabilitiesAxis=us-gaap_RecoverableVacationPayMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**wtr_RegulatoryAssetsAndLiabilitiesAxis=wtr_FairValueAdjustmentOfLongTermDebtAssumedInAcquisitionMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**wtr_RegulatoryAssetsAndLiabilitiesAxis=wtr_RateCaseFilingExpensesAndOtherMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**wtr_RegulatoryAssetsAndLiabilitiesAxis=wtr_WaterTankPaintingMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |