| **Pension Plans And Other Post-Retirement Benefits (Components Of Net Periodic Benefit Costs) (Details) (USD $)In Thousands, unless otherwise specified** | 12 Months Ended                                                                                                                                                                                 |
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| Pension Benefits [Member]                                                                                                                                 |                                                                                                                                                                                            |   |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                                                                                          |                                                                                                                                                                                            |   |   |
| Service cost                                                                                                                                              | $ 4,295us-gaap_DefinedBenefitPlanServiceCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember                                           | $ 5,313us-gaap_DefinedBenefitPlanServiceCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember | $ 4,920us-gaap_DefinedBenefitPlanServiceCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember |
| Interest cost                                                                                                                                             | 14,153us-gaap_DefinedBenefitPlanInterestCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember                                           | 12,660us-gaap_DefinedBenefitPlanInterestCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember | 12,728us-gaap_DefinedBenefitPlanInterestCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember |
| Expected return on plan assets                                                                                                                            | (17,601)us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember                           | (14,770)us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember | (13,588)us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember |
| Amortization of prior service cost                                                                                                                        | 277us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember                      | 228us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember | 277us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember |
| Amortization of actuarial loss                                                                                                                            | 2,256wtr_DefinedBenefitPlanAmortizationOfActuarialLoss/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember                                 | 8,169wtr_DefinedBenefitPlanAmortizationOfActuarialLoss/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember | 6,568wtr_DefinedBenefitPlanAmortizationOfActuarialLoss/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember |
| Settlement loss                                                                                                                                           |                                                                                                                                                                                            |   | 304wtr_DefinedBenefitPlanSettlementCharge/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember |
| Curtailment loss                                                                                                                                          | 84wtr_DefinedBenefitPlanCurtailmentCharge/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember                                              |   |   |
| Net periodic benefit cost                                                                                                                                 | 3,464us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember                                  | 11,600us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember | 11,209us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember |
| Other Postretirement Benefits [Member]                                                                                                                    |                                                                                                                                                                                            |   |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                                                                                          |                                                                                                                                                                                            |   |   |
| Service cost                                                                                                                                              | 1,161us-gaap_DefinedBenefitPlanServiceCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember                          | 1,525us-gaap_DefinedBenefitPlanServiceCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember | 1,309us-gaap_DefinedBenefitPlanServiceCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember |
| Interest cost                                                                                                                                             | 2,903us-gaap_DefinedBenefitPlanInterestCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember                         | 2,579us-gaap_DefinedBenefitPlanInterestCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember | 2,482us-gaap_DefinedBenefitPlanInterestCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember |
| Expected return on plan assets                                                                                                                            | (2,742)us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember         | (2,268)us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember | (1,950)us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember |
| Amortization of prior service cost                                                                                                                        | (278)us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember | (295)us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember | (299)us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember |
| Amortization of actuarial loss                                                                                                                            | 260wtr_DefinedBenefitPlanAmortizationOfActuarialLoss/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember                | 1,479wtr_DefinedBenefitPlanAmortizationOfActuarialLoss/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember | 1,024wtr_DefinedBenefitPlanAmortizationOfActuarialLoss/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember |
| Amortization of regulatory asset                                                                                                                          |                                                                                                                                                                                            |   | 69wtr_DefinedBenefitPlanAmortizationOfRegulatoryAssets/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember |
| Settlement loss                                                                                                                                           |                                                                                                                                                                                            |   | 90wtr_DefinedBenefitPlanSettlementCharge/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember |
| Net periodic benefit cost                                                                                                                                 | $ 1,304us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember             | $ 3,020us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember | $ 2,725us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
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| - Definition
The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
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| - Definition
An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Glossary Expected Return on Plan Assets -URI http://asc.fasb.org/extlink&oid=6512136Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Glossary Expected Return on Plan Assets -URI http://asc.fasb.org/extlink&oid=6512171Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
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| - Definition
The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920
+ Details**Name:**us-gaap_DefinedBenefitPlanInterestCost**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
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| - Definition
The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920
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| - Definition
The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Service Cost (Component of Net Periodic Pension Cost) -URI http://asc.fasb.org/extlink&oid=6525008Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920
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| X                                                                                                                                                                                                                                                                                      |
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| - Definition
Defined benefit plan amortization of actuarial loss.
+ References
No definition available.
+ Details**Name:**wtr_DefinedBenefitPlanAmortizationOfActuarialLoss**Namespace Prefix:**wtr_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Defined benefit plan amortization of regulatory assets.
+ References
No definition available.
+ Details**Name:**wtr_DefinedBenefitPlanAmortizationOfRegulatoryAssets**Namespace Prefix:**wtr_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Defined benefit plan curtailment charge
+ References
No definition available.
+ Details**Name:**wtr_DefinedBenefitPlanCurtailmentCharge**Namespace Prefix:**wtr_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Defined benefit plan settlement charge.
+ References
No definition available.
+ Details**Name:**wtr_DefinedBenefitPlanSettlementCharge**Namespace Prefix:**wtr_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
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