Regulatory Matters - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Regulatory matters:
Net regulatory Assets	$ 80,052,000	$ 69,507,000
GSWC
Regulatory matters:
Net regulatory Assets	53,314,000	45,729,000
BVES
Regulatory matters:
Regulatory Asset -incremental vegetation management costs	13,300,000
Regulatory asset- wildfire mitigation plans (WMP)	6,600,000
Golden State Water Company and Bear Valley Electric Service Inc.
Regulatory matters:
Regulatory asset not accruing carrying costs	61,300,000
2022/2023 general rate case memorandum accounts (unbilled revenue) | GSWC
Regulatory matters:
Net regulatory Assets	$ 46,527,000	52,795,000
Amortization period	36 months
Water revenue adjustment mechanism, net of modified cost balancing account
Regulatory matters:
Increase (decrease) in other regulatory assets	$ 15,300,000
Regulatory asset recovery periods	24 months
Water revenue adjustment mechanism, net of modified cost balancing account | GSWC
Regulatory matters:
Net regulatory Assets	$ 50,842,000	41,545,000
Commercial paper, term	90 days
Regulatory asset recovery periods	18 months
Deferred Income Tax Charge [Member] | GSWC
Regulatory matters:
Net regulatory Assets	$ (69,567,000)	(70,189,000)
Deferred Income Tax Charge [Member] | Golden State Water Company and Bear Valley Electric Service Inc.
Regulatory matters:
Regulatory asset not accruing carrying costs	73,300,000
Derivative instrument memorandum account (Note 5)
Regulatory matters:
Regulatory asset not accruing carrying costs	5,600,000
Derivative instrument memorandum account (Note 5) | BVES
Regulatory matters:
Net regulatory Assets	5,593,000	2,360,000
Pension Costs and Other Postretirement Benefit Costs [Member] | GSWC
Regulatory matters:
Net regulatory Assets	(4,828,000)	(4,867,000)
Pension Costs and Other Postretirement Benefit Costs [Member] | Golden State Water Company and Bear Valley Electric Service Inc.
Regulatory matters:
Regulatory asset not accruing carrying costs	3,500,000
Modified Cost Balancing account ("MCBA") | GSWC
Regulatory matters:
Net regulatory Assets	(3,800,000)
Water Revenue Adjustment Mechanism ("WRAM")
Regulatory matters:
Deferred Revenue, Revenue Recognized	0
Water Revenue Adjustment Mechanism ("WRAM") | GSWC
Regulatory matters:
Net regulatory Assets	54,600,000
Electric Supply Cost Adjustment Mechanism | BVES
Regulatory matters:
Net regulatory Assets	777,000	2,583,000
Low income rate assistance balancing accounts | GSWC
Regulatory matters:
Net regulatory Assets	7,747,000	5,763,000
Flowed-through deferred income taxes, net | GSWC
Regulatory matters:
Net regulatory Assets	5,667,000	$ 3,190,000
Flowed-through deferred income taxes, net | Golden State Water Company and Bear Valley Electric Service Inc.
Regulatory matters:
Net regulatory Assets	$ 7,200,000