Commitments and Contingencies - Estimated Range of Possible Remediation Costs (Details) - Minnesota and Indiana Gas Service Territories $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)
Loss Contingencies [Line Items]
Liability recorded for remediation of Minnesota sites	$ 16
Minimum
Loss Contingencies [Line Items]
Site Contingency Loss Exposure	$ 11
Years to resolve contingency	5 years
Maximum
Loss Contingencies [Line Items]
Site Contingency Loss Exposure	$ 58
Years to resolve contingency	50 years
CERC Corp
Loss Contingencies [Line Items]
Liability recorded for remediation of Minnesota sites	$ 11
CERC Corp | Minimum
Loss Contingencies [Line Items]
Site Contingency Loss Exposure	$ 8
Years to resolve contingency	30 years
CERC Corp | Maximum
Loss Contingencies [Line Items]
Site Contingency Loss Exposure	$ 36
Years to resolve contingency	50 years