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Subsequent Events (Details) - ASUS	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Subsequent Event [Line Items]
Period of fixed price contracts to operate and maintain the water and/or wastewater systems at various military bases	50 years
Contracts
Subsequent Event [Line Items]
Period of fixed price contracts to operate and maintain the water and/or wastewater systems at various military bases		50 years

X

- Definition

Represents the period of fixed price contracts to operate and maintain the water and/or wastewater systems at various military bases.

+ References

No definition available.

+ Details

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Namespace Prefix:	awr_
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Balance Type:	na
Period Type:	duration

X

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

X

- Details

Name:	dei_LegalEntityAxis=awr_AmericanStatesUtilityServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=awr_ContractedServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: