v3.26.1
Regulatory Matters - Narrative (Details) - USD ($)
$ in Thousands
 3 Months Ended
Apr. 08, 2026
Mar. 31, 2026
Dec. 31, 2025
Regulatory matters:      
Net regulatory Assets   $ 92 $ 9,264
Golden State Water Company and Bear Valley Electric Service Inc.      
Regulatory matters:      
Net regulatory Assets   100  
Regulatory asset   122,500  
Regulatory liability   122,400  
Regulatory asset not accruing carrying costs   44,700  
Regulatory liabilities not accruing carrying costs   $ 118,300  
Commercial paper, term   90 days  
Golden State Water Company and Bear Valley Electric Service Inc. | Deferred Income Tax Charge      
Regulatory matters:      
Regulatory liabilities not accruing carrying costs   $ 66,900  
Golden State Water Company and Bear Valley Electric Service Inc. | Pension Costs and Other Postretirement Benefit Costs      
Regulatory matters:      
Regulatory liabilities not accruing carrying costs   41,000  
Golden State Water Company and Bear Valley Electric Service Inc. | PFAS Contamination Litigation Proceeds Memorandum Account      
Regulatory matters:      
Regulatory liabilities not accruing carrying costs   10,400  
GSWC      
Regulatory matters:      
Net regulatory Assets   (41,788) (36,994)
GSWC | Tyco | Subsequent Event      
Regulatory matters:      
Litigation settlement, amount awarded $ 2,200    
GSWC | Deferred Income Tax Charge      
Regulatory matters:      
Net regulatory Assets   (63,152) (63,223)
GSWC | Pension Costs and Other Postretirement Benefit Costs      
Regulatory matters:      
Net regulatory Assets   (43,984) (43,479)
GSWC | PFAS Contamination Litigation Proceeds Memorandum Account      
Regulatory matters:      
Net regulatory Assets   (10,406) (10,987)
BVES      
Regulatory matters:      
Net regulatory Assets   41,880 46,258
Flowed-through deferred income taxes, net | Golden State Water Company and Bear Valley Electric Service Inc.      
Regulatory matters:      
Regulatory asset not accruing carrying costs   25,800  
Flowed-through deferred income taxes, net | GSWC      
Regulatory matters:      
Net regulatory Assets   22,286 20,932
Derivative instrument memorandum account (Note 5)      
Regulatory matters:      
Regulatory asset not accruing carrying costs   15,700  
Derivative instrument memorandum account (Note 5) | BVES      
Regulatory matters:      
Net regulatory Assets   15,708 15,503
Other Regulatory assets | Golden State Water Company and Bear Valley Electric Service Inc.      
Regulatory matters:      
Regulatory asset not accruing carrying costs   3,200  
2022/2023 general rate case memorandum accounts (unbilled revenue) | GSWC      
Regulatory matters:      
Net regulatory Assets   18,814 22,107
2023/2024 General Rate Case Memorandum accounts ( unbilled revenue) | BVES      
Regulatory matters:      
Net regulatory Assets   7,237 8,221
Wildfire mitigation and other fire prevention related costs memorandum accounts | BVES      
Regulatory matters:      
Net regulatory Assets   $ 9,877 $ 11,336