Regulatory Matters - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	$ 54,679,000	$ 69,507,000
Golden State Water Company and Bear Valley Electric Service, Inc.
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	54,700,000
Regulatory assets	149,800,000
Regulatory liability	$ 95,100,000
Commercial paper, term	90 days
Regulatory asset not accruing carrying costs	$ 26,300,000
Regulatory liabilities not accruing carrying costs	92,100,000
GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	$ 18,173,000	$ 45,729,000
Discount percentage for qualified low income water customers	20.00%
GSWC | Cost of capital proceeding
Schedule of Regulatory Assets and Liabilities [Line Items]
Approved equity capital structure, percentage		57.00%
Approved debt capital structure, percentage		43.00%
Cost of debt, percentage		5.10%
Approved return on equity, percentage		8.85%
Term for the cost of capital proceeding		3 years
Revenue impact due to lower cost of debt		$ 6,400,000
BVES
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	$ 36,506,000	23,778,000
Discount percentage for qualified low income water customers	20.00%
Incremental vegetation management costs	$ 9,900,000
Regulatory asset wildfire mitigation plans WMP	4,800,000
Flowed-through deferred income taxes, net (Note 11) | Golden State Water Company and Bear Valley Electric Service, Inc.
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset not accruing carrying costs	14,300,000
Flowed-through deferred income taxes, net (Note 11) | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets	12,506,000	3,190,000
Derivative instrument memorandum account (Note 5)
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset not accruing carrying costs	8,800,000
Derivative instrument memorandum account (Note 5) | BVES
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets	8,823,000	2,360,000
Other Regulatory Assets | Golden State Water Company and Bear Valley Electric Service, Inc.
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset not accruing carrying costs	3,200,000
Other Regulatory Assets | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets	11,352,000	10,661,000
Other Regulatory Assets | BVES
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets	8,853,000	10,280,000
Excess deferred income taxes (Note 11)
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	67,500,000
Pensions and other post-retirement obligations (Note 12) | Golden State Water Company and Bear Valley Electric Service, Inc.
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities not accruing carrying costs	23,500,000
Pensions and other post-retirement obligations (Note 12) | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets	23,500,000
Pensions and other post-retirement obligations (Note 12) | GSWC | Under Collection in Two Way Pension Balancing Account
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	1,700,000
Other Regulatory Liabilities | Golden State Water Company and Bear Valley Electric Service, Inc.
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities not accruing carrying costs	1,100,000
2022/2023 general rate case memorandum accounts (unbilled revenue) | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	37,700,000
Regulatory assets	$ 37,711,000	52,795,000
Water revenue adjustment mechanism, net of the modified cost balancing account
Schedule of Regulatory Assets and Liabilities [Line Items]
Recovery period	18 months
Water revenue adjustment mechanism, net of the modified cost balancing account | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	$ 29,700,000
Regulatory assets	$ 29,738,000	41,545,000
Commercial paper, term	90 days
Recovery period	24 months
Water Revenue Adjustment Mechanism
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory adjustment increase (decrease)	$ 8,000,000.0
Deferred revenues	0
Water Revenue Adjustment Mechanism | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	29,100,000
Modified Cost Balancing Account | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	600,000
Low income rate assistance balancing accounts | Golden State Water Company and Bear Valley Electric Service, Inc.
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	8,800,000
Low income rate assistance balancing accounts | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets	8,834,000	5,763,000
Wildfire mitigation and other fire prevention related costs memorandum accounts | BVES
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets	$ 14,681,000	17,716,000
Regulatory asset, amortization period	36 months
Filing term for the Wildfire Mitigation and Other Fire Prevention related costs balancing and memorandum accounts	90 days
2023/2024 general rate case memorandum accounts (unbilled revenue) | BVES
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	$ 9,800,000
Regulatory assets	$ 9,777,000	$ 0
Regulatory asset, amortization period	36 months
Filing term for the Wildfire Mitigation and Other Fire Prevention related costs balancing and memorandum accounts	90 days