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Commitments And Contingencies (Tables)
 3 Months Ended
Mar. 31, 2021
Commitments and Contingencies [Line Items]  
Other Purchase Commitments At March 31, 2021, related minimum future commitments were as follows (in millions):
Alliant EnergyIPLWPL
Natural gas$958$466$492
Coal945539
Other (a)1226030
$1,174$581$561

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2021.
MGP Site Estimated Future Costs And Recorded Liabilities At March 31, 2021, 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). At March 31, 2021, such amounts for WPL were not material.
Alliant EnergyIPL
Range of estimated future costs$9 
-
$25$7 
-
$19
Current and non-current environmental liabilities$13$9
IPL [Member]  
Commitments and Contingencies [Line Items]  
Other Purchase Commitments At March 31, 2021, related minimum future commitments were as follows (in millions):
Alliant EnergyIPLWPL
Natural gas$958$466$492
Coal945539
Other (a)1226030
$1,174$581$561

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2021.
MGP Site Estimated Future Costs And Recorded Liabilities At March 31, 2021, 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). At March 31, 2021, such amounts for WPL were not material.
Alliant EnergyIPL
Range of estimated future costs$9 
-
$25$7 
-
$19
Current and non-current environmental liabilities$13$9
WPL [Member]  
Commitments and Contingencies [Line Items]  
Other Purchase Commitments At March 31, 2021, related minimum future commitments were as follows (in millions):
Alliant EnergyIPLWPL
Natural gas$958$466$492
Coal945539
Other (a)1226030
$1,174$581$561

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2021.