Represents the term associated with a fixed-term security.

No definition available.

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

- Definition

Represents amount billed to customers as surcharges.

+ References

No definition available.

+ Details

Name:	awr_RegulatoryAssetAmountBilledToCustomersAsSurcharges
Namespace Prefix:	awr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the recovery periods of the surcharge billed to the customers.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

The increase (decrease) during the reporting period in the value of other assets that are created when regulatory agencies permits public utilities to defer costs to the balance sheet.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

+ Details

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

- Definition

The net amount of all regulatory assets less all regulatory liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

+ Details

Name:	us-gaap_NetRegulatoryAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_RegulatoryAssetAxis=awr_WaterRevenueAdjustmentMechanismNetOfModifiedCostBalancingAccountMember
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:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAssetAxis=awr_WaterRevenueAdjustmentMechanismMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAssetAxis=awr_ModifiedCostBalancingAccountMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Regulatory Matters: Alternative-Revenue Programs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Water Revenue Adjustment Mechanism and Modified Cost Balancing Account
Regulatory matters:
Increase (decrease) in other regulatory assets			$ 13,000
GOLDEN STATE WATER COMPANY
Regulatory matters:
Regulatory assets	$ 6,036		$ 6,036		$ (2,450)
GOLDEN STATE WATER COMPANY \| Water Revenue Adjustment Mechanism and Modified Cost Balancing Account
Regulatory matters:
Commercial paper, term			90 days
Amount billed to customers as surcharges	3,800	$ 832	$ 6,100	$ 3,600
Regulatory assets	29,495		$ 29,495		$ 22,535
GOLDEN STATE WATER COMPANY \| Water Revenue Adjustment Mechanism and Modified Cost Balancing Account \| Minimum
Regulatory matters:
Regulatory Asset Recovery Periods			12 months
GOLDEN STATE WATER COMPANY \| Water Revenue Adjustment Mechanism and Modified Cost Balancing Account \| Maximum
Regulatory matters:
Regulatory Asset Recovery Periods			24 months
GOLDEN STATE WATER COMPANY \| Water Revenue Adjustment Mechanism [Member]
Regulatory matters:
Regulatory assets	15,700		$ 15,700
GOLDEN STATE WATER COMPANY \| Modified Cost Balancing Account
Regulatory matters:
Regulatory assets	$ 13,800		$ 13,800