Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) item unit
Contingencies
Environmental Loss Contingency Statement OfFinancial Position Extensible Enumeration Not Disclosed Flag	estimated remaining cost
American States Utility Services | Contracted services:
Contingencies
Number of the contracts with 15-year contracts with the U.S. government | unit	1
American States Utility Services | Contracted services: | Minimum
Contingencies
Period of Fixed Price Contracts to Operate and Maintain Water Systems at Various Military Bases	15 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
Environmental Costs Recognized, Capitalized	$ 6.8
Amount paid by the State of California Underground Storage Tank Fund for clean-up and remediation of plant facilities	1.5
Accrued liability for the estimated additional cost to complete the clean-up at the site	$ 1.3