v3.26.1
CREDIT LOSSES - ROLLFORWARD OF ALLOWANCES (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Accounts Receivable, Allowance for Credit Loss [Roll Forward]        
Balance at beginning of period $ 156.0 $ 159.4 $ 148.7 $ 162.8
Provision for credit losses 63.4 35.4 128.9 68.0
Write-offs charged against the allowance (59.2) (54.8) (119.8) (114.9)
Recoveries of amounts previously written off 19.9 24.4 41.9 53.6
Balance at end of period 148.9 142.2 148.9 142.2
Change in allowance for credit losses       (20.6)
Uncollectible expense        
Accounts Receivable, Allowance for Credit Loss [Roll Forward]        
Provision for credit losses deferred for future recovery or refund (31.2) (22.2) (50.8) (27.3)
Public Utilities        
Accounts Receivable, Allowance for Credit Loss [Roll Forward]        
Balance at beginning of period     148.7  
Balance at end of period 148.9   148.9  
Wisconsin | Public Utilities        
Accounts Receivable, Allowance for Credit Loss [Roll Forward]        
Balance at beginning of period 63.6 60.9 61.7 73.6
Provision for credit losses 50.5 21.7 99.3 37.8
Write-offs charged against the allowance (39.9) (38.5) (75.9) (72.3)
Recoveries of amounts previously written off 12.9 13.9 27.2 26.2
Balance at end of period 61.2 52.3 61.2 52.3
Wisconsin | Public Utilities | Uncollectible expense        
Accounts Receivable, Allowance for Credit Loss [Roll Forward]        
Provision for credit losses deferred for future recovery or refund (25.9) (5.7) (51.1) (13.0)
Illinois | Public Utilities        
Accounts Receivable, Allowance for Credit Loss [Roll Forward]        
Balance at beginning of period 88.3 93.2 82.3 83.9
Provision for credit losses 12.5 13.4 29.3 29.7
Write-offs charged against the allowance (18.6) (15.7) (42.1) (41.3)
Recoveries of amounts previously written off 6.8 10.2 13.9 26.6
Balance at end of period 83.7 84.6 83.7 84.6
Illinois | Public Utilities | Uncollectible expense        
Accounts Receivable, Allowance for Credit Loss [Roll Forward]        
Provision for credit losses deferred for future recovery or refund (5.3) (16.5) 0.3 (14.3)
Other States | Public Utilities        
Accounts Receivable, Allowance for Credit Loss [Roll Forward]        
Balance at beginning of period 4.1 5.3 4.7 5.3
Provision for credit losses 0.4 0.3 0.3 0.5
Write-offs charged against the allowance (0.7) (0.6) (1.8) (1.3)
Recoveries of amounts previously written off 0.2 0.3 0.8 0.8
Balance at end of period 4.0 5.3 4.0 5.3
Other States | Public Utilities | Uncollectible expense        
Accounts Receivable, Allowance for Credit Loss [Roll Forward]        
Provision for credit losses deferred for future recovery or refund $ 0.0 $ 0.0 $ 0.0 $ 0.0