CREDIT LOSSES - ROLLFORWARD OF ALLOWANCES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 166.9	$ 178.7	$ 193.5	$ 199.3
Provision for credit losses	23.8	14.8	73.4	46.9
Write-offs charged against the allowance	(46.2)	(47.7)	(170.4)	(152.7)
Recovery of amounts previously written off	17.7	14.1	54.8	43.2
Balance at end of period	155.0	176.8	155.0	176.8
Change in allowance for credit losses			38.5	22.5
Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	(7.2)	16.9	3.7	40.1
Public Utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period			193.5
Balance at end of period	155.0		155.0
Wisconsin | Public Utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	68.7	76.4	77.4	82.0
Provision for credit losses	12.6	10.2	36.2	28.1
Write-offs charged against the allowance	(30.8)	(31.8)	(102.3)	(89.8)
Recovery of amounts previously written off	9.6	7.4	31.7	25.4
Balance at end of period	63.9	72.0	63.9	72.0
Wisconsin | Public Utilities | Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	3.8	9.8	20.9	26.3
Illinois | Public Utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	93.2	97.0	109.7	111.0
Provision for credit losses	11.5	4.0	38.8	17.3
Write-offs charged against the allowance	(12.9)	(14.4)	(63.2)	(58.7)
Recovery of amounts previously written off	6.1	6.3	18.8	16.6
Balance at end of period	86.9	100.0	86.9	100.0
Illinois | Public Utilities | Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	(11.0)	7.1	(17.2)	13.8
Other States | Public Utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	5.0	5.3	6.4	6.3
Provision for credit losses	(0.3)	0.6	(1.6)	1.5
Write-offs charged against the allowance	(2.5)	(1.5)	(4.9)	(4.2)
Recovery of amounts previously written off	2.0	0.4	4.3	1.2
Balance at end of period	4.2	4.8	4.2	4.8
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