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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&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://www.xbrl.org/2003/role/presentationRef
-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:	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_RegulatoryAssetAxis=awr_ModifiedCostBalancingAccountMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Regulatory Matters: Alternative-Revenue Programs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Apr. 08, 2019	Dec. 31, 2018
Water Revenue Adjustment Mechanism and Modified Cost Balancing Account
Regulatory matters:
Increase (decrease) in other regulatory assets	$ 10,000
GOLDEN STATE WATER COMPANY
Regulatory matters:
Under (over) collection	$ (23,726)			$ (28,340)
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	$ 2,800	$ 4,200
Under (over) collection	$ 24,998			$ 17,763
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 \| Modified Cost Balancing Account
Regulatory matters:
Under (over) collection	$ 14,900
Subsequent Event [Member] \| GOLDEN STATE WATER COMPANY \| WRAM
Regulatory matters:
Under (over) collection			$ 20,400