v3.26.1
CREDIT LOSSES - GROSS RECEIVABLES AND RELATED ALLOWANCES (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Mar. 31, 2026
Dec. 31, 2025
Jun. 30, 2025
Mar. 31, 2025
Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 1,678.1   $ 2,211.4      
Allowance for credit losses 148.9 $ 156.0 148.7 $ 142.2 $ 159.4 $ 162.8
Accounts receivable and unbilled revenues, net 1,529.2   2,062.7      
Total accounts receivable, net - past due greater than 90 days $ 134.0   $ 89.8      
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms 93.90%   89.90%      
Amount of net accounts receivable with regulatory protections $ 882.1          
Percent of net accounts receivable with regulatory protections 57.70%          
Public Utilities            
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 1,601.2   $ 2,153.8      
Allowance for credit losses 148.9   148.7      
Accounts receivable and unbilled revenues, net 1,452.3   2,005.1      
Total accounts receivable, net - past due greater than 90 days $ 134.0   $ 89.8      
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms 93.90%   89.90%      
Wisconsin | Public Utilities            
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 1,136.8   $ 1,368.8      
Allowance for credit losses 61.2 63.6 61.7 52.3 60.9 73.6
Accounts receivable and unbilled revenues, net 1,075.6   1,307.1      
Total accounts receivable, net - past due greater than 90 days $ 64.5   $ 46.4      
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms 94.40%   94.60%      
Illinois | Public Utilities            
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 401.5   $ 654.8      
Allowance for credit losses 83.7 88.3 82.3 84.6 93.2 83.9
Accounts receivable and unbilled revenues, net 317.8   572.5      
Total accounts receivable, net - past due greater than 90 days $ 65.0   $ 36.8      
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms 100.00%   100.00%      
Other States | Public Utilities            
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 62.9   $ 130.2      
Allowance for credit losses 4.0 $ 4.1 4.7 $ 5.3 $ 5.3 $ 5.3
Accounts receivable and unbilled revenues, net 58.9   125.5      
Total accounts receivable, net - past due greater than 90 days $ 4.5   $ 6.6      
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms 0.00%   0.00%      
Non-Utility Energy Infrastructure            
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 71.3   $ 50.3      
Allowance for credit losses 0.0   0.0      
Accounts receivable and unbilled revenues, net 71.3   50.3      
Total accounts receivable, net - past due greater than 90 days $ 0.0   $ 0.0      
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms 0.00%   0.00%      
Corporate and Other            
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 5.6   $ 7.3      
Allowance for credit losses 0.0   0.0      
Accounts receivable and unbilled revenues, net 5.6   7.3      
Total accounts receivable, net - past due greater than 90 days $ 0.0   $ 0.0      
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms 0.00%   0.00%