Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	$ (13,971)	$ 9,264
GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	(53,663)	(36,994)
GSWC | Deferred Income Tax Charge
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liability	(63,081)	(63,223)
GSWC | Pension Costs and Other Postretirement Benefit Costs
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liability	(44,502)	(43,479)
GSWC | PFAS Contamination Litigation Proceeds Memorandum Account
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liability	(16,851)	(10,987)
GSWC | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liability	(212)	(1,331)
BVES
Schedule of Regulatory Assets and Liabilities [Line Items]
Net regulatory assets	39,692	46,258
BVES | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liability	(4,206)	(4,015)
2022/2023 general rate case memorandum accounts (unbilled revenue) | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset	14,632	22,107
Flowed-through deferred income taxes, net | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset	24,260	20,932
Low income rate assistance balancing accounts | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset	11,881	10,582
Other regulatory assets | GSWC
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset	20,210	28,405
Other regulatory assets | BVES
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset	13,676	15,213
Derivative instrument memorandum account (Note 5) | BVES
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset	14,631	15,503
2023/2024 general rate case memorandum accounts (unbilled revenue) | BVES
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset	6,624	8,221
Wildfire mitigation and other fire prevention related costs memorandum accounts | BVES
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory asset	$ 8,967	$ 11,336