Credit Losses - Rollforward of Allowances (Details) - Utility - 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 January 1	$ 49.7	$ 51.4	$ 59.3
Provision for credit losses	23.8	27.3	24.8
Write-offs charged against the allowance	(94.1)	(83.4)	(47.6)
Recoveries of amounts previously written off	19.4	20.4	15.2
Balance at December 31	44.5	49.7	51.4
Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	$ 45.7	$ 34.0	$ (0.3)