Enviromental matters (Details 2)	12 Months Ended
	Dec. 31, 2021 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	823,000
Environmental matters accrual for site remediation	419,000
Incurred Costs For Site Remedial Investigation	505,000
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	7,600,000
Incurred costs for site remedial investigation and feasibility study	5,300,000
Environmental matters accrual of investigative costs	2,300,000
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