Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 163,066	$ 155,328	$ 311,079	$ 290,579
GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Total operating revenues	119,697	110,424	221,700	200,689
Water: \| GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	119,685	97,645	221,432	183,435
Total operating revenues	119,697	110,424	221,700	200,689
Electric: \| BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	13,164	8,895	26,940	21,642
Total operating revenues	12,928	8,703	27,930	20,908
Contracted services: \| ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	30,441	36,201	61,449	68,982
Tariff-based revenues \| Water: \| GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	117,240	96,065	217,571	180,726
Tariff-based revenues \| Electric: \| BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	11,780	8,866	25,513	21,539
CPUC-approved surcharges (cost-recovery activities) \| Water: \| GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	1,756	912	2,561	1,459
CPUC-approved surcharges (cost-recovery activities) \| Electric: \| BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	1,384	29	1,427	103
Other \| Water: \| GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	689	668	1,300	1,250
Alternative revenues program \| Water: \| GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Alternative revenue programs, net	12	12,779	268	17,254
Alternative revenues program \| Electric: \| BVES
Disaggregation of Revenue [Line Items]
Alternative revenue programs, net	(236)	(192)	990	(734)
Water \| Contracted services: \| ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	14,398	21,603	31,010	43,170
Wastewater \| Contracted services: \| ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 16,043	$ 14,598	$ 30,439	$ 25,812