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Commitments and Contingencies Environmental Requirements - Water and Waste (Details)
$ in Millions
Jun. 30, 2022
USD ($)
Plant
Period
Federal Coal Ash Regulation  
Site Contingency [Line Items]  
Number of sites where regulated ash units will still be in operation at a specified date | Period 8
Federal Coal Ash Regulation | PSCo  
Site Contingency [Line Items]  
Number of sites where statistically significant increases over established groundwater standards exist | Period 4
Number of sites where corrective action options are being evaluated for locations with statistically significant increases above background concentrations 2
Estimated cost to remediate groundwater sampling results $ 35
Estimated cost of construction of an alternative collection and treatment system 25
EPA Penalty 1
Federal Coal Ash Regulation | PSCo | Minimum [Member]  
Site Contingency [Line Items]  
Cost of Beneficial Use Coal Ash Project 30
Federal Coal Ash Regulation | PSCo | Maximum [Member]  
Site Contingency [Line Items]  
Cost of Beneficial Use Coal Ash Project 40
Federal Clean Water Act Section 316 (b) | Capital Addition Purchase Commitments  
Site Contingency [Line Items]  
Liability for estimated cost to comply with regulation $ 40
Federal Clean Water Act Section 316 (b) | NSP-Minnesota  
Site Contingency [Line Items]  
Minimum number of plants which could be required to make improvements to reduce entrainment | Plant 6
Federal Clean Water Act Section 316 (b) | NSP-Wisconsin  
Site Contingency [Line Items]  
Minimum number of plants which could be required to make improvements to reduce entrainment | Plant 2