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

No definition available.

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

- Definition

Represents the term of the debt instrument.

+ References

No definition available.

+ Details

Name:	awr_DebtInstrumentMaturityTerm
Namespace Prefix:	awr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Ratio of Indebtedness to EBITDA

+ References

No definition available.

+ Details

Name:	awr_RatioofIndebtednesstoEBITDA
Namespace Prefix:	awr_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ 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 210.5-02.22(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

- 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_DebtInstrumentLineItems
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

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

The cash inflow from a debt initially having maturity due after one year or beyond the 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 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

+ Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=awr_NotesPayable3.45PercentDue2029Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=awr_GoldenStateWaterCompanyMember
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=awr_PrivatePlacementNotesMember
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_LongtermDebtTypeAxis=awr_AmericanRecoveryAndReinvestmentActObligationDue2033Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Long-Term Debt 3 (Details)	12 Months Ended
Long-Term Debt 3 (Details)	Dec. 31, 2017 USD ($)	Dec. 31, 2016	Dec. 31, 2014 USD ($)	Oct. 31, 2009 USD ($)
Notes Payable 3.45 Percent Due 2029 [Member]
Long-term debt
Interest rate (as a percent)	3.45%	3.45%
GSWC
Long-term debt
Ratio of Indebtedness to EBITDA	2.5
GSWC \| Maximum
Long-term debt
Ratio of Indebtedness to EBITDA	8
GSWC \| Private Placement Notes [Member]
Long-term debt
Debt Instrument Covenant Interest Coverage Ratio	400.00%
GSWC \| Private Placement Notes [Member] \| Minimum [Member]
Long-term debt
Debt Instrument Covenant Interest Coverage Ratio	200.00%
GSWC \| Notes Payable 3.45 Percent Due 2029 [Member]
Long-term debt
Debt Instrument, Face Amount	$ 15,000,000		$ 15,000,000
Interest rate (as a percent)	3.45%	3.45%	3.45%
GSWC \| American Recovery and Reinvestment Act Obligation due 2033
Long-term debt
Maximum amount of loan that can be borrowed				$ 9,000,000.0
Interest rate (as a percent)	2.50%
Maturity term	20 years
Loan proceeds received for reimbursement of costs of conversion	$ 8,600,000
GSWC \| American Recovery and Reinvestment Act Obligation due 2033 \| Letters of credit to CDHP
Long-term debt
Amount of debt issued	$ 5,400,000.0