Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 161,782	$ 151,696	$ 452,361	$ 470,519
GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Total operating revenues	124,043	116,231	324,732	345,851
Water: | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	121,356	104,006	304,791	305,186
Total operating revenues	124,043	116,231	324,732	345,851
Electric: | BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	8,919	8,562	30,561	30,820
Total operating revenues	9,040	8,956	29,948	30,688
Contracted services: | ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	28,699	26,509	97,681	93,980
Tariff-based revenues | Water: | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	119,716	102,225	300,442	301,144
Tariff-based revenues | Electric: | BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	8,892	8,424	30,431	30,416
CPUC-approved surcharges (cost-recovery activities) | Water: | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	946	1,107	2,405	1,982
CPUC-approved surcharges (cost-recovery activities) | Electric: | BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	27	138	130	404
Other | Water: | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	694	674	1,944	2,060
Alternative revenues program | Water: | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Alternative revenue programs, net	2,687	12,225	19,941	40,665
Alternative revenues program | Electric: | BVES
Disaggregation of Revenue [Line Items]
Alternative revenue programs, net	121	394	(613)	(132)
Water | Contracted services: | ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	14,651	16,504	57,821	58,103
Wastewater | Contracted services: | ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 14,048	$ 10,005	$ 39,860	$ 35,877