Credit Losses - Rollforward of Allowances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Year	$ 199.3	$ 198.3	$ 220.1
Provision for credit losses	72.0	86.1	75.7
Write-offs charged against the allowance	(223.6)	(206.0)	(129.8)
Recovery of amounts previously written off	57.5	58.0	45.4
Balance at End of Year	193.5	199.3	198.3
Change in allowance for credit losses	5.8	1.0
Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	88.3	62.9	(13.1)
Public utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Year	199.3
Balance at End of Year	193.5	199.3
Wisconsin | Public utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Year	82.0	84.0	102.1
Provision for credit losses	40.9	50.5	46.4
Write-offs charged against the allowance	(131.6)	(117.0)	(74.8)
Recovery of amounts previously written off	33.6	34.8	26.9
Balance at End of Year	77.4	82.0	84.0
Wisconsin | Public utilities | Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	52.5	29.7	(16.6)
Illinois | Public utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Year	111.0	105.5	111.6
Provision for credit losses	26.3	33.0	25.6
Write-offs charged against the allowance	(85.4)	(82.6)	(52.5)
Recovery of amounts previously written off	22.0	21.9	17.3
Balance at End of Year	109.7	111.0	105.5
Illinois | Public utilities | Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	35.8	33.2	3.5
Other States | Public utilities
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Year	6.3	8.8	6.4
Provision for credit losses	4.8	2.6	3.7
Write-offs charged against the allowance	(6.6)	(6.4)	(2.5)
Recovery of amounts previously written off	1.9	1.3	1.2
Balance at End of Year	6.4	6.3	8.8
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