Bank Debt (Details) - USD ($)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Short-term borrowing activities (excluding letters of credit)
Balance outstanding at the end of the period	$ 28,000,000	$ 0
Syndicated revolving credit facility
Bank debt
Increase in additional aggregate bank commitments	$ 50,000,000.0
Variable rate basis	Euro rate
Syndicated revolving credit facility \| Minimum
Short-term borrowing activities (excluding letters of credit)
Interest coverage ratio	325.00%
Syndicated revolving credit facility \| Maximum
Short-term borrowing activities (excluding letters of credit)
Total funded debt ratio	65.00%
Letters of credit \| Letter of Credit Irrevocable Franchise Agreement with City of Rancho Cordova [Member]
Bank debt
Letter of credit, amount	$ 15,000,000
AWR
Bank debt
Maximum borrowing capacity	100,000,000.0
Short-term borrowing activities (excluding letters of credit)
Balance outstanding at the end of the period	28,000,000	$ 0
AWR \| Syndicated revolving credit facility
Bank debt
Increase in additional aggregate bank commitments	$ 50,000,000.0
Short-term borrowing activities (excluding letters of credit)
Interest coverage ratio	768.00%
Total funded debt ratio	44.00%
AWR \| Syndicated revolving credit facility \| Minimum
Short-term borrowing activities (excluding letters of credit)
Interest coverage ratio	325.00%
AWR \| Syndicated revolving credit facility \| Maximum
Short-term borrowing activities (excluding letters of credit)
Total funded debt ratio	65.00%
AWR \| Syndicated revolving credit facility \| Letters of credit
Bank debt
Maximum borrowing capacity	$ 25,000,000
Letter of credit, amount	$ 10,400,000
Letter of credit fee (as a percent)	0.65%

Represents the funded debt ratio required to be maintained for debt instrument.

No definition available.

Name:	awr_DebtInstrumentCovenantFundedDebtRatio
Namespace Prefix:	awr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the interest coverage ratio required to be maintained for debt instrument.

+ References

No definition available.

+ Details

Name:	awr_DebtInstrumentCovenantInterestCoverageRatio
Namespace Prefix:	awr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the maximum amount of additional bank commitments the entity may elect to increase under terms of the debt agreement.

+ References

No definition available.

+ Details

Name:	awr_LineOfCreditFacilityElectiveMaximumAdditionalBorrowingCapacity
Namespace Prefix:	awr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

-- None. No documentation exists for this element. --

+ References

No definition available.

+ Details

Name:	awr_ScheduleOfDebtInstrumentsLineItems
Namespace Prefix:	awr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentDescriptionOfVariableRateBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Current portion of the total carrying amount as of the balance sheet date due within one year or the operating cycle, if longer, on all notes payable to banks paid on an installment with long term maturities. This can include the amount of any loans from the applicant firm. This does not, however, include any mortgage balances.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(a)(1),20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_NotesPayableToBankCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_ShortTermBorrowingsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_CreditFacilityAxis=awr_SyndicatedRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=awr_LetterofCreditIrrevocableFranchiseAgreementwithCityofRanchoCordovaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=us-gaap_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: