Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) item
Contingencies
Environmental Loss Contingency Statement OfFinancial Position Extensible Enumeration Not Disclosed Flag	estimated remaining cost
Contracted services: | Maximum
Contingencies
Period of Fixed Price Contracts to Operate and Maintain Water Systems at Various Military Bases	50 years
American States Utility Services | Contracted services: | Maximum
Contingencies
Period of Fixed Price Contracts to Operate and Maintain Water Systems at Various Military Bases	50 years
Environmental Clean-Up and Remediation | GSWC
Contingencies
Number of Plant Sites | item	1
Amount paid by the State of California Underground Storage Tank Fund for clean-up and remediation of plant facilities	$ 1.5
Environmental Costs Recognized, Capitalized	6.3
Accrued liability for the estimated additional cost to complete the clean-up at the site	$ 1.3