CREDIT LOSSES - ROLLFORWARD OF ALLOWANCES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 159.4	$ 190.7	$ 162.8	$ 193.5
Provision for credit losses	35.4	23.7	68.0	49.6
Write-offs charged against the allowance	(54.8)	(59.3)	(114.9)	(124.2)
Recovery of amounts previously written off	24.4	17.9	53.6	37.1
Balance at end of period	142.2	166.9	142.2	166.9
Change in allowance for credit losses			20.6	26.6
Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	(22.2)	(6.1)	(27.3)	10.9
Public Utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period			162.8
Balance at end of period	142.2		142.2
Wisconsin | Public Utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	60.9	83.0	73.6	77.4
Provision for credit losses	21.7	9.8	37.8	23.6
Write-offs charged against the allowance	(38.5)	(35.9)	(72.3)	(71.5)
Recovery of amounts previously written off	13.9	10.4	26.2	22.1
Balance at end of period	52.3	68.7	52.3	68.7
Wisconsin | Public Utilities | Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	(5.7)	1.4	(13.0)	17.1
Illinois | Public Utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	93.2	104.6	83.9	109.7
Provision for credit losses	13.4	12.2	29.7	27.3
Write-offs charged against the allowance	(15.7)	(22.3)	(41.3)	(50.3)
Recovery of amounts previously written off	10.2	6.2	26.6	12.7
Balance at end of period	84.6	93.2	84.6	93.2
Illinois | Public Utilities | Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	(16.5)	(7.5)	(14.3)	(6.2)
Other States | Public Utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	5.3	3.1	5.3	6.4
Provision for credit losses	0.3	1.7	0.5	(1.3)
Write-offs charged against the allowance	(0.6)	(1.1)	(1.3)	(2.4)
Recovery of amounts previously written off	0.3	1.3	0.8	2.3
Balance at end of period	5.3	5.0	5.3	5.0
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