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Commitments And Contingencies (Tables)
 12 Months Ended
Dec. 31, 2023
Long-term Purchase Commitment [Line Items]  
Other Purchase Commitments At December 31, 2023, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but will require payment when electricity is generated by the provider, were as follows (in millions):
Alliant Energy20242025202620272028ThereafterTotal
Natural gas$301$187$123$78$49$142$880
Coal9449886—165
Other (a)6117149222125
$456$253$145$95$57$164$1,170
IPL20242025202620272028ThereafterTotal
Natural gas$165$86$47$35$14$25$372
Coal4935886—106
Other (a)2322222253
$237$123$57$45$22$47$531
WPL20242025202620272028ThereafterTotal
Natural gas$136$101$76$43$35$117$508
Coal4514————59
Other (a)2311———25
$204$116$77$43$35$117$592

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2023.
Schedule of Environmental Liabilities At December 31, 2023, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the
MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):
Alliant EnergyIPLWPL
Range of estimated future costs$9 -$36$5 -$11$4 -$25
Current and non-current environmental liabilities$18$8$10
IPL [Member]  
Long-term Purchase Commitment [Line Items]  
Other Purchase Commitments At December 31, 2023, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but will require payment when electricity is generated by the provider, were as follows (in millions):
Alliant Energy20242025202620272028ThereafterTotal
Natural gas$301$187$123$78$49$142$880
Coal9449886—165
Other (a)6117149222125
$456$253$145$95$57$164$1,170
IPL20242025202620272028ThereafterTotal
Natural gas$165$86$47$35$14$25$372
Coal4935886—106
Other (a)2322222253
$237$123$57$45$22$47$531
WPL20242025202620272028ThereafterTotal
Natural gas$136$101$76$43$35$117$508
Coal4514————59
Other (a)2311———25
$204$116$77$43$35$117$592

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2023.
Schedule of Environmental Liabilities At December 31, 2023, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the
MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):
Alliant EnergyIPLWPL
Range of estimated future costs$9 -$36$5 -$11$4 -$25
Current and non-current environmental liabilities$18$8$10
WPL [Member]  
Long-term Purchase Commitment [Line Items]  
Other Purchase Commitments At December 31, 2023, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but will require payment when electricity is generated by the provider, were as follows (in millions):
Alliant Energy20242025202620272028ThereafterTotal
Natural gas$301$187$123$78$49$142$880
Coal9449886—165
Other (a)6117149222125
$456$253$145$95$57$164$1,170
IPL20242025202620272028ThereafterTotal
Natural gas$165$86$47$35$14$25$372
Coal4935886—106
Other (a)2322222253
$237$123$57$45$22$47$531
WPL20242025202620272028ThereafterTotal
Natural gas$136$101$76$43$35$117$508
Coal4514————59
Other (a)2311———25
$204$116$77$43$35$117$592

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2023.