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Summary of Significant Accounting Policies: (Details) customer in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) customer registrant	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Basis of Presentation:
Number of registrants filing combined report \| registrant			2
Related Party Transactions
Notes payable to bank	$ 70,000,000		$ 70,000,000		$ 0
AWR \| Syndicated Credit Facility
Related Party Transactions
Maximum borrowing capacity on line of credit	150,000,000		150,000,000
Golden State Water Company
Related Party Transactions
Payments to affiliate for corporate office administrative and general costs	1,200,000	$ 1,000,000	3,200,000	$ 3,000,000
Golden State Water Company \| Notes Payable 6.7 Percent Due 2019
Related Party Transactions
Notes outstanding	$ 40,000,000		$ 40,000,000
Interest rate	6.70%		6.70%
Golden State Water Company \| Water Service Utility Operations
Nature of Operations:
Number of customers \| customer			260
Golden State Water Company \| Electric Service Utility Operations
Nature of Operations:
Number of customers \| customer			24
American States Utility Services \| Contracted Services
Nature of Operations:
Period of fixed price contracts to operate and maintain the water and/or wastewater systems at various military bases			50 years
Fort Riley \| Contracted Services
Nature of Operations:
Period of fixed price contracts to operate and maintain the water and/or wastewater systems at various military bases				50 years