CREDIT LOSSES - ROLLFORWARD OF ALLOWANCES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 175.8	$ 231.7	$ 198.3	$ 220.1
Provision for credit losses	15.8	15.9	57.9	53.6
Write-offs charged against the allowance	(49.4)	(46.8)	(148.1)	(89.7)
Recovery of amounts previously written off	13.5	10.6	43.3	33.1
Balance at end of period	168.5	199.7	168.5	199.7
Change in allowance for credit losses			29.8
Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	12.8	(11.7)	17.1	(17.4)
Utility Operations
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period			198.3
Balance at end of period	168.5		168.5
Wisconsin | Utility Operations
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	78.0	114.4	84.0	102.1
Provision for credit losses	10.0	10.7	33.6	33.8
Write-offs charged against the allowance	(34.6)	(16.2)	(85.5)	(51.2)
Recovery of amounts previously written off	8.8	5.7	26.7	19.8
Balance at end of period	72.4	76.4	72.4	76.4
Wisconsin | Utility Operations | Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	10.2	(38.2)	13.6	(28.1)
Illinois | Utility Operations
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	91.0	109.0	105.5	111.6
Provision for credit losses	5.2	4.4	23.6	16.7
Write-offs charged against the allowance	(13.5)	(29.9)	(58.7)	(36.7)
Recovery of amounts previously written off	4.4	4.7	15.8	12.4
Balance at end of period	89.7	114.7	89.7	114.7
Illinois | Utility Operations | Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	2.6	26.5	3.5	10.7
Other States | Utility Operations
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	6.8	8.3	8.8	6.4
Provision for credit losses	0.6	0.8	0.7	3.1
Write-offs charged against the allowance	(1.3)	(0.7)	(3.9)	(1.8)
Recovery of amounts previously written off	0.3	0.2	0.8	0.9
Balance at end of period	6.4	8.6	6.4	8.6
Other States | Utility Operations | 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