Environmental matters (Details 2) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)
Site Contingency [Line Items]
Total Estimated Costs For Site Remedial Investigation And Feasibility Study		$ 7.6
Incurred Costs For Site Remedial Investigation And Feasibility Study		5.4
Environmental Matters Accrual For Site Remediation, Period Increase	$ 11.1
Environmental Matters Accrual For Remedial Investigation and Feasibility Study Costs	2.2	2.2
Environmental Matters Accrual For Site Remediation	$ 17.5	17.5
Minimum [Member]
Site Contingency [Line Items]
Site Contingency, Loss Exposure Not Accrued, Best Estimate		13.6
Maximum [Member]
Site Contingency [Line Items]
Site Contingency, Loss Exposure Not Accrued, Best Estimate		$ 71.0