CONSOLIDATED STATEMENTS OF CAPITALIZATION (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Capitalization, Long-term Debt and Equity	$ 850,984	$ 815,278
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares outstanding	36,571,360	36,571,360
GSWC
Capitalization, Long-term Debt and Equity	$ 795,413	$ 767,751
Common stock, shares authorized	1,000	1,000
Common stock, shares outstanding	146	146
6.81% notes due 2028
Interest rate per annum (as a percent)	6.81%	6.81%
6.81% notes due 2028 \| GSWC
Interest rate per annum (as a percent)	6.81%	6.81%
6.59% notes due 2029
Interest rate per annum (as a percent)	6.59%	6.59%
6.59% notes due 2029 \| GSWC
Interest rate per annum (as a percent)	6.59%	6.59%
7.875% notes due 2030
Interest rate per annum (as a percent)	7.875%	7.875%
7.875% notes due 2030 \| GSWC
Interest rate per annum (as a percent)	7.875%	7.875%
7.23% notes due 2031
Interest rate per annum (as a percent)	7.23%	7.23%
7.23% notes due 2031 \| GSWC
Interest rate per annum (as a percent)	7.23%	7.23%
6.00% notes due 2041
Interest rate per annum (as a percent)	6.00%	6.00%
6.00% notes due 2041 \| GSWC
Interest rate per annum (as a percent)	6.00%	6.00%
3.45% private placement notes due 2029
Interest rate per annum (as a percent)	3.45%	3.45%
3.45% private placement notes due 2029 \| GSWC
Interest rate per annum (as a percent)	3.45%	3.45%
9.56% private placement notes due 2031
Interest rate per annum (as a percent)	9.56%	9.56%
9.56% private placement notes due 2031 \| GSWC
Interest rate per annum (as a percent)	9.56%	9.56%
Notes Payable 5.87 Percent Due 2028 [Member]
Interest rate per annum (as a percent)	5.87%	5.87%
Notes Payable 5.87 Percent Due 2028 [Member] \| GSWC
Interest rate per annum (as a percent)	5.87%	5.87%
6.70% private placement notes due 2019
Interest rate per annum (as a percent)	6.70%	6.70%
6.70% private placement notes due 2019 \| GSWC
Interest rate per annum (as a percent)	6.70%	6.70%
5.50% tax-exempt obligation due 2026
Interest rate per annum (as a percent)	5.50%	5.50%
5.50% tax-exempt obligation due 2026 \| GSWC
Interest rate per annum (as a percent)	5.50%	5.50%

This element represents the total consolidated (as applicable) capitalization of the entity which is comprised of its long-term debt and equity instruments. The table may be detailed by subsidiary (legal entity) and include information by type of debt or equity detailed by instrument.

No definition available.

+ Details

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

- Definition

The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

+ References

+ Details

Name:	us-gaap_CommonStockSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

+ 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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644

+ Details

Name:	us-gaap_CommonStockSharesOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=awr_NotesPayable6.81PercentDue2028Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=awr_NotesPayable6.59PercentDue2029Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=awr_NotesPayable7.875PercentDue2030Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=awr_NotesPayable7.23PercentDue2031Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=awr_NotesPayable6PercentDue2041Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=awr_NotesPayable9.56PercentDue2031Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=awr_NotesPayable5.87PercentDue2028Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=awr_NotesPayable6.7PercentDue2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=awr_NotesPayable5.5PercentDue2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: