Other Commitments And Contingencies (Narrative) (Details) $ in Millions	12 Months Ended	28 Months Ended
	Dec. 31, 2021 USD ($) Rate MW	Dec. 31, 2020 USD ($)	Feb. 01, 2022 USD ($)
Other Commitments And Contingencies [Line Items]
Wind power purchase agreement capacity \| MW	500
Major Rail Operators	3
Line of Credit Facility, Amount Outstanding	$ 0.0	$ 0.0
Guarantor Obligations, Current Carrying Value	288.9	40.7
Recorded reserves to cover environmental remediation at various sites	$ 91.1	92.6
Wind Power Purchase Agreement, Purchase Percentage \| Rate	100.00%
Restructuring and Related Cost, Expected Cost	$ 42.0
Subsequent Event
Other Commitments And Contingencies [Line Items]
Guarantor Obligations, Current Carrying Value			$ 485.2
MGP Sites
Other Commitments And Contingencies [Line Items]
Number of waste disposal sites identified by program	54
Liability for estimated remediation costs	$ 85.1	85.0
Reasonably possible remediation costs variance from reserve	$ 17.0
Columbia Of Massachusetts
Other Commitments And Contingencies [Line Items]
Pipeline Replacement Expenses		258.0
Coal Transportation \| Maximum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year	2028
Pipeline Service Agreements [Member] \| Maximum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year	2038
Pipeline Service Agreements [Member] \| Minimum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year	2022
IT Service Agreements [Member] \| Maximum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year	2027
Standby Letters of Credit
Other Commitments And Contingencies [Line Items]
Line of Credit Facility, Amount Outstanding	$ 18.9	$ 15.2