Regulatory Matters - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Regulatory matters:
Regulatory asset not accruing carrying costs	$ (62,800,000)
Net regulatory Assets	77,569,000	$ 69,507,000
Regulatory asset amount billed to customers as surcharges	0
GSWC
Regulatory matters:
Net regulatory Assets	51,548,000	45,729,000
BVES
Regulatory matters:
Regulatory Asset -incremental vegetation management costs	12,500,000
Regulatory asset- wildfire mitigation plans (WMP)	6,200,000
2022/2023 general rate case memorandum accounts (unbilled revenue) | GSWC
Regulatory matters:
Net regulatory Assets	$ 50,010,000	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	$ 8,000,000
Regulatory asset recovery periods	24 months
Water revenue adjustment mechanism, net of modified cost balancing account | GSWC
Regulatory matters:
Net regulatory Assets	$ 47,529,000	41,545,000
Commercial paper, term	90 days
Deferred Income Tax Charge [Member]
Regulatory matters:
Regulatory asset not accruing carrying costs	$ (73,700,000)
Deferred Income Tax Charge [Member] | GSWC
Regulatory matters:
Net regulatory Assets	(69,878,000)	(70,189,000)
Derivative instrument memorandum account (Note 5)
Regulatory matters:
Regulatory asset not accruing carrying costs	(6,200,000)
Derivative instrument memorandum account (Note 5) | BVES
Regulatory matters:
Net regulatory Assets	6,168,000	2,360,000
Pension Costs and Other Postretirement Benefit Costs [Member]
Regulatory matters:
Regulatory asset not accruing carrying costs	(3,700,000)
Pension Costs and Other Postretirement Benefit Costs [Member] | GSWC
Regulatory matters:
Net regulatory Assets	(4,861,000)	(4,867,000)
Modified Cost Balancing account ("MCBA") | GSWC
Regulatory matters:
Net regulatory Assets	(2,500,000)
Water Revenue Adjustment Mechanism ("WRAM") | GSWC
Regulatory matters:
Net regulatory Assets	50,000,000
Electric Supply Cost Adjustment Mechanism | BVES
Regulatory matters:
Net regulatory Assets	2,268,000	2,583,000
Low income rate assistance balancing accounts | GSWC
Regulatory matters:
Net regulatory Assets	6,846,000	5,763,000
Flowed-through deferred income taxes, net
Regulatory matters:
Net regulatory Assets	5,600,000
Flowed-through deferred income taxes, net | GSWC
Regulatory matters:
Net regulatory Assets	$ 4,348,000	$ 3,190,000