| **Employee Stock And Incentive Plan (Summary Of Value Of Restricted Stock Units) (Details) - Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Thousands** | 12 Months Ended |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                                           |            |   |   |
| Weighted average fair value of stock awards granted                                                                                                                          | $ 32.08         | $ 26.00 | $ 24.80 |
| Intrinsic value of vested RSUs                                                                                                                                               | $ 805           | $ 2,327 | $ 759 |
| Fair value of vested RSUs                                                                                                                                                    | $ 605           | $ 1,904 | $ 544 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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| 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.
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| X                                                                                                                                                                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Share-Based Compensation Arrangement By Share-Based Payment Award Fair Value Assumptions Fair Value Of Vested Shares
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Share-Based Compensation Arrangement By Share-Based Payment Award Fair Value Assumptions Intrinsic Value Of Vested Shares
+ References
No definition available.
+ Details**Name:**wtr_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsIntrinsicValueOfVestedShares**Namespace Prefix:**wtr_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |