Consolidated Statements Of Cash Flow (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net income	$ 48,545us-gaap_NetIncomeLoss	$ 42,859us-gaap_NetIncomeLoss
Income from discontinued operations		458
Income from continuing operations	48,545	42,401
Adjustments to reconcile income from continuing operations to net cash flows from operating activities:
Depreciation and amortization	31,349	32,114
Deferred income taxes	2,688us-gaap_DeferredIncomeTaxExpenseBenefit	3,692us-gaap_DeferredIncomeTaxExpenseBenefit
Provision for doubtful accounts	936us-gaap_ProvisionForDoubtfulAccounts	1,508us-gaap_ProvisionForDoubtfulAccounts
Stock-based compensation	1,341us-gaap_ShareBasedCompensation	1,331us-gaap_ShareBasedCompensation
(Gain) loss on sale of other assets	(169)us-gaap_GainLossOnSaleOfOtherAssets	348us-gaap_GainLossOnSaleOfOtherAssets
Net change in receivables, inventory and prepayments	191	3,644
Net change in payables, accrued interest, accrued taxes and other accrued liabilities	11,460	13,269
Other	(6,321)	(7,833)
Operating cash flows from continuing operations	90,020	90,474
Operating cash flows used in discontinued operations, net		(545)
Net cash flows from operating activities	90,020	89,929
Cash flows from investing activities:
Property, plant and equipment additions, including the debt component of allowance for funds used during construction of $296 and $367	(70,284)	(59,819)
Acquisitions of utility systems and other, net	(788)	(4,045)
Release of funds previously restricted for construction activity	32
Net proceeds from the sale of utility system and other assets	232	133
Other	(1,180)	(91)
Investing cash flows used in continuing operations	(71,988)	(63,822)
Investing cash flows from discontinued operations, net		39
Net cash flows used in investing activities	(71,988)	(63,783)
Cash flows from financing activities:
Customers' advances and contributions in aid of construction	1,193	1,142
Repayments of customers' advances	(1,040)	(234)
Net (repayments) proceeds of short-term debt	14,664	(8,827)
Proceeds from long-term debt	52,629	73,192
Repayments of long-term debt	(29,800)us-gaap_RepaymentsOfLongTermDebt	(31,874)us-gaap_RepaymentsOfLongTermDebt
Change in cash overdraft position	(21,431)	(21,753)
Proceeds from exercised stock options	2,852	2,757
Stock-based compensation windfall tax benefits	1,230	964
Repurchase of common stock	(3,754)	(1,973)
Dividends paid on common stock	(29,176)us-gaap_PaymentsOfDividendsCommonStock	(26,873)us-gaap_PaymentsOfDividendsCommonStock
Other	(263)	(181)
Financing cash flows used in continuing operations	(12,896)	(13,660)
Financing cash flows used in discontinued operations, net		(36)
Net cash flows used in financing activities	(12,896)	(13,696)
Net change in cash and cash equivalents	5,136	12,450
Cash and cash equivalents at beginning of period	4,138	5,058
Cash and cash equivalents at end of period	9,274	17,508
Noncash Investing and Financing Items [Abstract]
Property, plant and equipment additions purchased at the period end, but not yet paid for	$ 20,158	$ 18,550

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+ References

+ Details

Name:	us-gaap_PaymentsOfDividendsCommonStock
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

+ References

+ Details

Name:	us-gaap_PaymentsToAcquirePropertyPlantAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for the purchase of waste water systems which includes the waste treatment and disposal facility and equipment to households and industry.

+ References

+ Details

Name:	us-gaap_PaymentsToAcquireWasteWaterSystems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from borrowing by the entity from developers, builders, government agencies and municipalities for construction that are repaid in cash, generally on a straight-line basis over periods ranging from five to forty years.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

+ Details

Name:	us-gaap_ProceedsFromAdvancesForConstruction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ References

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 9

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The net cash inflow or outflow from the excess drawing from an existing cash balance, which will be honored by the bank but reflected as a loan to the drawer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 9

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585

+ Details

Name:	us-gaap_ProceedsFromRepaymentsOfBankOverdrafts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The net cash inflow or outflow for borrowing having initial term of repayment within one year or the normal operating cycle, if longer.

+ References

+ Details

Name:	us-gaap_ProceedsFromRepaymentsOfShortTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (j)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromStockOptionsExercised
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of expense related to write-down of receivables to the amount expected to be collected. Includes, but is not limited to, accounts receivable and notes receivable.

+ References

+ Details

Name:	us-gaap_ProvisionForDoubtfulAccounts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow for the payments made by the entity, generally on a straight-line basis over periods ranging from five to forty years to developers, builders, government agencies and municipalities for borrowings received in construction.

+ References

+ Details

Name:	us-gaap_RepaymentsOfAdvancesForConstruction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

Name:	us-gaap_RepaymentsOfLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Proceeds from sale of utility system and other

+ References

No definition available.

+ Details

Name:	wtr_ProceedsFromSaleOfUtilitySystemAndOther
Namespace Prefix:	wtr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration