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Enviromental matters (Details 2)
 12 Months Ended
Dec. 31, 2022
USD ($)
Portland Harbor Site  
Site Contingency [Line Items]  
Environmental matters investigative costs $ 115,000,000
Environmental matters, estimated costs 1,000,000,000
Missoula, MT manufactured gas plant site  
Site Contingency [Line Items]  
Total estimated costs for site remediation 560,000
Environmental Matters Estimated Investigative Costs 1,800,000
Environmental matters accrual for site remediation 725,000
Incurred Costs For Site Remedial Investigation 922,000
Bremerton, WA manufactured gas plant site  
Site Contingency [Line Items]  
Environmental matters accrual for site remediation 17,500,000
Total estimated costs for site remedial investigation and feasibility study 12,100,000
Incurred costs for site remedial investigation and feasibility study 9,900,000
Environmental matters accrual of investigative costs 2,200,000
Bellingham, WA manufactured gas plant site  
Site Contingency [Line Items]  
Site contingency, loss exposure not accrued, preferred alternative estimate 9,300,000
Minimum | Bremerton, WA manufactured gas plant site  
Site Contingency [Line Items]  
Site contingency, loss exposure not accrued, best estimate 13,600,000
Minimum | Bellingham, WA manufactured gas plant site  
Site Contingency [Line Items]  
Site contingency, loss exposure not accrued, best estimate 8,000,000
Maximum | Bremerton, WA manufactured gas plant site  
Site Contingency [Line Items]  
Site contingency, loss exposure not accrued, best estimate 71,000,000
Maximum | Bellingham, WA manufactured gas plant site  
Site Contingency [Line Items]  
Site contingency, loss exposure not accrued, best estimate $ 20,400,000