Regulatory Matters - Regulatory Assets, Net (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Regulatory assets:
Total regulatory assets	$ 245,276	$ 242,227
Less: current regulatory assets	12,626	18,172
Total regulatory assets, less current portion	232,650	224,055
Regulatory liabilities:
Total regulatory liabilities	508,982	484,841
Less: current regulatory liabilities	2	1,122
Total regulatory liabilities, less current portion	$ 508,980	483,719
Minimum
Regulatory assets:
Estimated service lives of assets	5 years
Maximum
Regulatory assets:
Estimated service lives of assets	100 years
Cost of removal
Regulatory liabilities:
Total regulatory liabilities	$ 379,624	364,398
Future income tax benefits due to customers
Regulatory liabilities:
Total regulatory liabilities	83,326	84,128
Unrecognized pensions and other postretirement benefits
Regulatory liabilities:
Total regulatory liabilities	27,696	27,872
PFAS legal settlement proceeds
Regulatory liabilities:
Total regulatory liabilities	6,352	0
Employee benefit costs
Regulatory liabilities:
Total regulatory liabilities	4,933	1,137
Water supply costs
Regulatory liabilities:
Total regulatory liabilities	4,405	3,386
Revenue adjustment mechanisms
Regulatory liabilities:
Total regulatory liabilities	2	1,122
Other
Regulatory liabilities:
Total regulatory liabilities	2,644	2,798
Future income tax benefits due to customers
Regulatory assets:
Total regulatory assets	185,239	180,103
Monterey Water Revenue Adjustment Mechanism (“MWRAM”)
Regulatory assets:
Total regulatory assets	14,753	9,985
Business combinations debt premium
Regulatory assets:
Total regulatory assets	11,043	12,313
Employee benefit costs
Regulatory assets:
Total regulatory assets	6,144	6,370
Revenue adjustment mechanisms
Regulatory assets:
Total regulatory assets	5,780	5,024
Customer Assistance Program ("CAP") balancing account
Regulatory assets:
Total regulatory assets	4,686	6,599
Unrecognized pensions and other postretirement benefits
Regulatory assets:
Total regulatory assets	1,506	3,177
2022 general rate case interim memorandum account
Regulatory assets:
Total regulatory assets	1,106	3,392
Other
Regulatory assets:
Total regulatory assets	$ 15,019	$ 15,264