Revenues Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Operating revenues	$ 595,459	$ 595,699	$ 491,528
GSWC
Disaggregation of Revenue [Line Items]
Operating revenues	417,410	433,473	340,602
GSWC | Water:
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	411,316	400,331	329,650
Operating revenues	417,410	433,473	340,602
GSWC | Water: | Tariff-based revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	405,756	394,623	324,838
GSWC | Water: | CPUC-approved surcharges (cost-recovery activities)
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	2,914	2,955	2,461
GSWC | Water: | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	2,646	2,753	2,351
GSWC | Water: | Alternative revenue program
Disaggregation of Revenue [Line Items]
Under/(over)-collection (alternative revenue program)	6,094	33,142	10,952
American States Utility Services | Contracted services:
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	126,404	120,394	110,940
American States Utility Services | Contracted services: | Water
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	72,951	75,785	68,626
American States Utility Services | Contracted services: | Wastewater
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	53,453	44,609	42,314
BVES | Electric:
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	50,801	40,697	39,894
Operating revenues	51,645	41,832	39,986
BVES | Electric: | Tariff-based revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	50,628	40,130	39,750
BVES | Electric: | CPUC-approved surcharges (cost-recovery activities)
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	173	567	144
BVES | Electric: | Alternative revenue program
Disaggregation of Revenue [Line Items]
Under/(over)-collection (alternative revenue program)	$ 844	$ 1,135	$ 92