Regulatory Matters - Narrative (Details)	3 Months Ended		12 Months Ended		15 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)	Sep. 30, 2022	Mar. 31, 2023 USD ($)	Apr. 10, 2023 USD ($)
Regulatory matters:
Regulatory asset not accruing carrying costs	$ 77,600,000				$ 77,600,000
Net Regulatory assets	17,626,000		$ (25,454,000)		17,626,000
Regulatory asset amount billed to customers as surcharges	0
GSWC
Regulatory matters:
Net Regulatory assets	$ 9,249,000		(26,574,000)		$ 9,249,000
Number of unresolved issues for 2022-2024 water General Rate Case	3				3
Number of customer service areas for the consolidation	2				2
Public Utilities, Approved Return on Equity, Percentage					8.90%
Regulatory asset-CEMA	$ 3,500,000				$ 3,500,000
GSWC | Cost of capital proceeding
Regulatory matters:
Revenue impact due to lower cost of debt	1,800,000	$ 1,400,000	1,100,000
BVES
Regulatory matters:
Regulatory Asset -incremental vegetation management costs	9,300,000				9,300,000
Regulatory asset-CEMA	500,000				500,000
Regulatory asset-Wildfire mitigation Plans ( WMP)	4,800,000				4,800,000
Regulatory asset CEMA - Storm	810,000				810,000
BVES | Subsequent Event [Member]
Regulatory matters:
Regulatory asset-CEMA						$ 0
Excess deferred income taxes
Regulatory matters:
Regulatory asset not accruing carrying costs	75,200,000				75,200,000
Excess deferred income taxes | GSWC
Regulatory matters:
Net Regulatory assets	(71,418,000)		(71,870,000)		(71,418,000)
Flowed-through income taxes | GSWC
Regulatory matters:
Net Regulatory assets	447,000		(1,134,000)		447,000
Derivative instrument memorandum account (Note 5)
Regulatory matters:
Regulatory asset not accruing carrying costs	6,700,000				6,700,000
Derivative instrument memorandum account (Note 5) | BVES
Regulatory matters:
Net Regulatory assets	(6,669,000)		(11,847,000)		(6,669,000)
Water revenue adjustment mechanism, net of the modified cost balancing account
Regulatory matters:
Increase (decrease) in other regulatory assets	$ 9,500,000		(9,800,000)
Regulatory asset recovery periods	24 months
Water revenue adjustment mechanism, net of the modified cost balancing account | GSWC
Regulatory matters:
Net Regulatory assets	$ 29,069,000		31,803,000		29,069,000
Commercial paper, term	90 days
Pension Costs and Other Postretirement Benefit Costs
Regulatory matters:
Regulatory asset not accruing carrying costs	$ 2,300,000				2,300,000
Water Revenue Adjustment Mechanism
Regulatory matters:
Net Regulatory assets	28,900,000				28,900,000
Modified Cost Balancing Account
Regulatory matters:
Net Regulatory assets	189,000				189,000
Cost of capital proceeding
Regulatory matters:
Net Regulatory assets	9,300,000				9,300,000
2022/2023 general rate case memorandum accounts (unbilled revenue) | GSWC
Regulatory matters:
Net Regulatory assets	$ 38,419,000		$ 0		$ 38,419,000
Cost of Capital, Proceeding for Water Regions [Member]
Regulatory matters:
Threshold percentage of Moody's average bond rate used adjusting return on equity and rate of return on rate base, Increase(Decrease)	0.0100
Adjust to return on equity	0.5
Cost of Capital, Proceeding for Water Regions [Member] | GSWC
Regulatory matters:
Public Utilities, Approved Return on Equity, Percentage	8.85%
Term for the cost of capital proceeding	3 years
Triggers for the WCMA adjustment, Impact of 103 Basis Point Increase in Moody's Rate, Percent				0.0103