Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 151,696	$ 134,984	$ 470,519	$ 366,161
GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Total operating revenues	116,231	100,799	345,851	265,561
Water: | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	104,006	92,295	305,186	250,840
Total operating revenues	116,231	100,799	345,851	265,561
Electric: | BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	8,562	8,920	30,820	29,912
Total operating revenues	8,956	8,919	30,688	29,028
Contracted services: | ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	26,509	25,266	93,980	71,572
Tariff-based revenues | Water: | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	102,225	90,998	301,144	247,108
Tariff-based revenues | Electric: | BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	8,424	8,891	30,416	29,824
Surcharges (cost-recovery activities) | Water: | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	1,107	672	1,982	2,018
Surcharges (cost-recovery activities) | Electric: | BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	138	29	404	88
Other | Water: | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	674	625	2,060	1,714
WRAM under/(over)-collection (alternative revenue program) | Water: | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Alternative revenue programs, net	12,225	8,504	40,665	14,721
WRAM under/(over)-collection (alternative revenue program) | Electric: | BVES
Disaggregation of Revenue [Line Items]
Alternative revenue programs, net	394	(1)	(132)	(884)
Water | Contracted services: | ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	16,504	16,142	58,103	43,862
Wastewater | Contracted services: | ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 10,005	$ 9,124	$ 35,877	$ 27,710