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Summary of Significant Accounting Policies: (Details) customer in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) customer registrant	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Summary of significant accounting policies
Earnings reinvested in the business	$ 323,818,000		$ 323,818,000				$ 0	$ 304,534,000
Operating lease right-of-use assets	11,058,000		$ 11,058,000				7,600,000	0
Basis of Presentation:
Number of registrants filing combined report \| registrant			2
Related Party Transactions
Notes payable to bank	185,500,000		$ 185,500,000					95,500,000
Total lease obligations	11,356,000		11,356,000				$ 8,000,000.0
AWR \| Syndicated Credit Facility
Related Party Transactions
Maximum borrowing capacity on line of credit						$ 200,000,000.0
GOLDEN STATE WATER COMPANY
Summary of significant accounting policies
Earnings reinvested in the business	222,179,000		222,179,000					211,163,000
Operating lease right-of-use assets	10,432,000		10,432,000					$ 0
Related Party Transactions
Payments to affiliate for corporate office administrative and general costs	$ 1,300,000	$ 1,000,000.0	$ 2,400,000	$ 2,000,000.0
GOLDEN STATE WATER COMPANY \| Notes Payable 6.7 Percent Due 2019 [Member]
Related Party Transactions
Debt and Capital Lease Obligations						$ 40,000,000.0
Debt Instrument, Interest Rate, Stated Percentage						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
ASUS \| Contracted Services
Nature of Operations:
Period of fixed price contracts to operate and maintain water systems at various military bases			50 years
Sales \| GOLDEN STATE WATER COMPANY \| Water Service Utility Operations
Nature of Operations:
Concentration Risk, Percentage			90.00%
Sales \| GOLDEN STATE WATER COMPANY \| Electric Service Utility Operations
Nature of Operations:
Concentration Risk, Percentage			85.00%
Minimum [Member] \| AWR \| Syndicated Credit Facility
Related Party Transactions
Line of Credit Facility, Current Borrowing Capacity						$ 150,000,000.0
Subsequent Event [Member] \| GOLDEN STATE WATER COMPANY \| Syndicated Credit Facility
Related Party Transactions
Debt Instrument, Face Amount					$ 115,000,000.0