Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 169,191	$ 148,013
GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Total operating revenues	113,110	102,003
Water: \| GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	112,227	101,747
Total operating revenues	113,110	102,003
Electric: \| BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	19,395	13,776
Total operating revenues	18,657	15,002
Contracted services: \| ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	37,424	31,008
Tariff-based revenues \| Water: \| GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	111,195	100,331
Tariff-based revenues \| Electric: \| BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	17,736	13,733
CPUC-approved surcharges (cost-recovery activities) \| Water: \| GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	414	805
CPUC-approved surcharges (cost-recovery activities) \| Electric: \| BVES
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	1,659	43
Other \| Water: \| GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	618	611
Alternative revenues program \| Water: \| GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Alternative revenue programs, net	883	256
Alternative revenues program \| Electric: \| BVES
Disaggregation of Revenue [Line Items]
Alternative revenue programs, net	(738)	1,226
Water \| Contracted services: \| ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	23,178	16,612
Wastewater \| Contracted services: \| ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 14,246	$ 14,396