| **Recent Accounting Pronouncements (Details) $ in Thousands**                    | Jan. 01, 2017 USD ($) |
|----------------------------------------------------------------------------------|-----------------------|
| Adjustments for New Accounting Principle, Early Adoption [Member]                |                  |
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]** |                  |
| Adjustment to retained earnings, before tax                                      | $ 982                 |

| 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_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
New Accounting Pronouncement Or Change In Accounting Principle, Cumulative Effect Of Change On Gross Equity Or Net Assets
+ References
No definition available.
+ Details**Name:**wtr_NewAccountingPronouncementOrChangeInAccountingPrincipleCumulativeEffectOfChangeOnGrossEquityOrNetAssets**Namespace Prefix:**wtr_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AdjustmentsForNewAccountingPrincipleEarlyAdoptionMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |