v3.26.3
CREDIT LOSSES - GROSS RECEIVABLES AND RELATED ALLOWANCES (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Jun. 30, 2026
Dec. 31, 2025
Sep. 30, 2025
Jun. 30, 2025
Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 1,543.7   $ 2,211.4      
Allowance for credit losses 139.9 $ 148.9 148.7 $ 129.5 $ 142.2 $ 162.8
Accounts receivable and unbilled revenues, net 1,403.8   2,062.7      
Total accounts receivable, net - past due greater than 90 days $ 124.8   $ 89.8      
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms 91.40%   89.90%      
Amount of net accounts receivable with regulatory protections $ 842.4          
Percent of net accounts receivable with regulatory protections 60.00%          
Public Utilities            
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 1,492.3   $ 2,153.8      
Allowance for credit losses 139.9   148.7      
Accounts receivable and unbilled revenues, net 1,352.4   2,005.1      
Total accounts receivable, net - past due greater than 90 days $ 124.8   $ 89.8      
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms 91.40%   89.90%      
Wisconsin | Public Utilities            
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 1,096.9   $ 1,368.8      
Allowance for credit losses 55.2 61.2 61.7 48.7 52.3 73.6
Accounts receivable and unbilled revenues, net 1,041.7   1,307.1      
Total accounts receivable, net - past due greater than 90 days $ 57.6   $ 46.4      
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms 94.00%   94.60%      
Illinois | Public Utilities            
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Accounts receivable and unbilled revenues $ 341.5   $ 654.8      
Allowance for credit losses 80.5 83.7 82.3 76.6 84.6 83.9
Accounts receivable and unbilled revenues, net 261.0   572.5      
Total accounts receivable, net - past due greater than 90 days $ 59.9   $ 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 $ 53.9   $ 130.2      
Allowance for credit losses 4.2 $ 4.0 4.7 $ 4.2 $ 5.3 $ 5.3
Accounts receivable and unbilled revenues, net 49.7   125.5      
Total accounts receivable, net - past due greater than 90 days $ 7.3   $ 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 $ 45.2   $ 50.3      
Allowance for credit losses 0.0   0.0      
Accounts receivable and unbilled revenues, net 45.2   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 $ 6.2   $ 7.3      
Allowance for credit losses 0.0   0.0      
Accounts receivable and unbilled revenues, net 6.2   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%