Credit Losses - Rollforward of Allowances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Year	$ 193.5	$ 199.3	$ 198.3
Provision for credit losses	104.9	72.0	86.1
Write-offs charged against the allowance	(243.4)	(223.6)	(206.0)
Recovery of amounts previously written off	72.0	57.5	58.0
Balance at End of Year	162.8	193.5	199.3
Change in allowance for credit losses	30.7	5.8	1.0
Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	35.8	88.3	62.9
Public utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Year	193.5
Balance at End of Year	162.8	193.5
Wisconsin | Public utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Year	77.4	82.0	84.0
Provision for credit losses	52.1	40.9	50.5
Write-offs charged against the allowance	(141.8)	(131.6)	(117.0)
Recovery of amounts previously written off	42.1	33.6	34.8
Balance at End of Year	73.6	77.4	82.0
Wisconsin | Public utilities | Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	43.8	52.5	29.7
Illinois | Public utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Year	109.7	111.0	105.5
Provision for credit losses	52.3	26.3	33.0
Write-offs charged against the allowance	(95.0)	(85.4)	(82.6)
Recovery of amounts previously written off	24.9	22.0	21.9
Balance at End of Year	83.9	109.7	111.0
Illinois | Public utilities | Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	(8.0)	35.8	33.2
Other States | Public utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Year	6.4	6.3	8.8
Provision for credit losses	0.5	4.8	2.6
Write-offs charged against the allowance	(6.6)	(6.6)	(6.4)
Recovery of amounts previously written off	5.0	1.9	1.3
Balance at End of Year	5.3	6.4	6.3
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