Commitments and Contingencies - Environmental Requirements - Water and Waste (Details) $ in Millions	Sep. 30, 2021 USD ($)
Federal Coal Ash Regulation
Site Contingency [Line Items]
Number of sites where regulated ash units will still be in operation at a specified date	5
Number of sites where statistically significant increases over established groundwater standards exist	4
Number of sites where corrective action options are being evaluated for locations with statistically significant increases above background concentrations	2
Number of sites where monitoring results indicate potential offsite impacts to groundwater	1
Number of facilities where alternative storage capacity options consistent with the CCR Rule are being pursued	1
Federal Coal Ash Regulation [Domain] | PSCo [Member]
Site Contingency [Line Items]
Estimated cost to remediate groundwater sampling results	$ 35
Estimated cost of construction of an alternative collection and treatment system	25
Estimated cost to close Comanche station bottom ash pond	$ 3