| **Consolidated Statements Of Capitalization (Parenthetical) - $ / shares** | 3 Months Ended | 12 Months Ended |
|----------------------------------------------------------------------------|----------------|-----------------|
||
| Common stock, par value                                                    | $ 0.50         | $ 0.50          |
| Revolving Credit Agreement, Due 2021 [Member]                              |           |            |
| Maturity date                                                              | 2023           | 2023            |
| Bank notes at 2.48% due 2019 [Member]                                      |           |            |
| Interest rate                                                              | 2.48%          | 2.48%           |
| Maturity date                                                              | 2019           | 2019            |
| Bank notes at 3.5% due 2020 [Member]                                       |           |            |
| Interest rate                                                              | 3.50%          | 3.50%           |
| Maturity date                                                              | 2020           | 2020            |
| Notes at 3.01% due 2027 [Member]                                           |           |            |
| Interest rate                                                              | 3.01%          | 3.01%           |
| Maturity date                                                              | 2027           | 2027            |
| Notes at 3.59% due 2041 [Member]                                           |           |            |
| Interest rate                                                              | 3.59%          | 3.59%           |
| Maturity date                                                              | 2041           | 2041            |
| Notes at 4.62% due 2019 [Member]                                           |           |            |
| Interest rate                                                              | 4.62%          | 4.62%           |
| Maturity date                                                              | 2019           | 2019            |
| Notes at 4.87% due 2024 [Member]                                           |           |            |
| Interest rate                                                              | 4.87%          | 4.87%           |
| Maturity date                                                              | 2024           | 2024            |
| Notes at 5.20% due 2020 [Member]                                           |           |            |
| Interest rate                                                              | 5.20%          | 5.20%           |
| Maturity date                                                              | 2020           | 2020            |
| Notes at 5.95% due 2037 [Member]                                           |           |            |
| Interest rate                                                              | 5.95%          | 5.95%           |
| Maturity date                                                              | 2037           | 2037            |
| Minimum [Member] | Long-Term Debt Of Subsidiaries 0.00% To 0.99% [Member]  |           |            |
| Interest rate                                                              | 0.00%          | 0.00%           |
| Maturity date                                                              | 2023           | 2023            |
| Minimum [Member] | Long-Term Debt Of Subsidiaries 1.00% To 1.99% [Member]  |           |            |
| Interest rate                                                              | 1.00%          | 1.00%           |
| Maturity date                                                              | 2019           | 2019            |
| Minimum [Member] | Long-Term Debt Of Subsidiaries 2.00% To 2.99% [Member]  |           |            |
| Interest rate                                                              | 2.00%          | 2.00%           |
| Maturity date                                                              | 2019           | 2019            |
| Minimum [Member] | Long-Term Debt Of Subsidiaries 3.00% To 3.99% [Member]  |           |            |
| Interest rate                                                              | 3.00%          | 3.00%           |
| Maturity date                                                              | 2019           | 2019            |
| Minimum [Member] | Long-Term Debt Of Subsidiaries 4.00% To 4.99% [Member]  |           |            |
| Interest rate                                                              | 4.00%          | 4.00%           |
| Maturity date                                                              | 2020           | 2020            |
| Minimum [Member] | Long-Term Debt Of Subsidiaries 5.00% To 5.99% [Member]  |           |            |
| Interest rate                                                              | 5.00%          | 5.00%           |
| Maturity date                                                              | 2019           | 2019            |
| Minimum [Member] | Long-Term Debt Of Subsidiaries 6.00% To 6.99% [Member]  |           |            |
| Interest rate                                                              | 6.00%          | 6.00%           |
| Maturity date                                                              | 2026           | 2026            |
| Minimum [Member] | Long-Term Debt Of Subsidiaries 7.00% To 7.99% [Member]  |           |            |
| Interest rate                                                              | 7.00%          | 7.00%           |
| Maturity date                                                              | 2022           | 2022            |
| Minimum [Member] | Long-Term Debt Of Subsidiaries 8.00% To 8.99% [Member]  |           |            |
| Interest rate                                                              | 8.00%          | 8.00%           |
| Maturity date                                                              | 2021           | 2021            |
| Minimum [Member] | Long-Term Debt Of Subsidiaries 9.00% To 9.99% [Member]  |           |            |
| Interest rate                                                              | 9.00%          | 9.00%           |
| Maturity date                                                              | 2020           | 2020            |
| Maximum [Member] | Long-Term Debt Of Subsidiaries 0.00% To 0.99% [Member]  |           |            |
| Interest rate                                                              | 0.99%          | 0.99%           |
| Maturity date                                                              | 2033           | 2033            |
| Maximum [Member] | Long-Term Debt Of Subsidiaries 1.00% To 1.99% [Member]  |           |            |
| Interest rate                                                              | 1.99%          | 1.99%           |
| Maturity date                                                              | 2035           | 2035            |
| Maximum [Member] | Long-Term Debt Of Subsidiaries 2.00% To 2.99% [Member]  |           |            |
| Interest rate                                                              | 2.99%          | 2.99%           |
| Maturity date                                                              | 2033           | 2033            |
| Maximum [Member] | Long-Term Debt Of Subsidiaries 3.00% To 3.99% [Member]  |           |            |
| Interest rate                                                              | 3.99%          | 3.99%           |
| Maturity date                                                              | 2056           | 2056            |
| Maximum [Member] | Long-Term Debt Of Subsidiaries 4.00% To 4.99% [Member]  |           |            |
| Interest rate                                                              | 4.99%          | 4.99%           |
| Maturity date                                                              | 2057           | 2057            |
| Maximum [Member] | Long-Term Debt Of Subsidiaries 5.00% To 5.99% [Member]  |           |            |
| Interest rate                                                              | 5.99%          | 5.99%           |
| Maturity date                                                              | 2043           | 2043            |
| Maximum [Member] | Long-Term Debt Of Subsidiaries 6.00% To 6.99% [Member]  |           |            |
| Interest rate                                                              | 6.99%          | 6.99%           |
| Maturity date                                                              | 2036           | 2036            |
| Maximum [Member] | Long-Term Debt Of Subsidiaries 7.00% To 7.99% [Member]  |           |            |
| Interest rate                                                              | 7.99%          | 7.99%           |
| Maturity date                                                              | 2027           | 2027            |
| Maximum [Member] | Long-Term Debt Of Subsidiaries 8.00% To 8.99% [Member]  |           |            |
| Interest rate                                                              | 8.99%          | 8.99%           |
| Maturity date                                                              | 2025           | 2025            |
| Maximum [Member] | Long-Term Debt Of Subsidiaries 9.00% To 9.99% [Member]  |           |            |
| Interest rate                                                              | 9.99%          | 9.99%           |
| Maturity date                                                              | 2026           | 2026            |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Face amount or stated value per share of common stock.
+ References
Reference 1: 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(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
+ Details**Name:**us-gaap_CommonStockParOrStatedValuePerShare**Namespace Prefix:**us-gaap_**Data Type:**num:perShareItemType**Balance Type:**na**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Contractual interest rate for funds borrowed, under the debt agreement.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
+ Details**Name:**us-gaap_DebtInstrumentInterestRateStatedPercentage**Namespace Prefix:**us-gaap_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**instant |
| X                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Debt Instrument, Maturity Date, Year
+ References
No definition available.
+ Details**Name:**wtr_DebtInstrumentMaturityDateYear**Namespace Prefix:**wtr_**Data Type:**xbrli:gYearItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_RevolvingCreditAgreementDueBMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_BankNoteBMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_BankNoteCMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_NotesBMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_NotesCMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_NotesDMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_NotesEMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_NotesFMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_NotesGMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**srt_RangeAxis=srt_MinimumMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_LongTermDebtOfSubsidiariesZeroPointZeroZeroPercentageToZeroPointNineNinePercentageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_LongTermDebtOfSubsidiariesOnePointZeroZeroPercentageToOnePointNineNinePercentageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_LongTermDebtOfSubsidiariesTwoPointZeroZeroPercentageToTwoPointNineNinePercentageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_LongTermDebtOfSubsidiariesThreePointZeroZeroPercentageToThreePointNineNinePercentageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_LongTermDebtOfSubsidiariesFourPointZeroZeroPercentageToFourPointNineNinePercentageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_LongTermDebtOfSubsidiariesFivePointZeroZeroPercentageToFivePointNineNinePercentageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_LongTermDebtOfSubsidiariesSixPointZeroZeroPercentageToSixPointNineNinePercentageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_LongTermDebtOfSubsidiariesSevenPointZeroZeroPercentageToSevenPointNineNinePercentageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_LongTermDebtOfSubsidiariesEightPointZeroZeroPercentageToEightPointNineNinePercentageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=wtr_LongTermDebtOfSubsidiariesNinePointZeroZeroPercentageToNinePointNineNinePercentageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**srt_RangeAxis=srt_MaximumMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |