CREDIT LOSSES - ROLLFORWARD OF ALLOWANCES (Details) - Utility segment - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 71.3	$ 45.7	$ 59.3	$ 38.1
Provision for credit losses	5.5	7.7	18.0	21.4
Write-offs charged against the allowance	(10.6)	(9.0)	(32.8)	(30.6)
Recovery of amounts previously written off	3.3	4.8	11.1	16.8
Balance at end of period	47.1	52.1	47.1	52.1
Uncollectible expense
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses deferred for future recovery or refund	$ (22.4)	$ 2.9	$ (8.5)	$ 6.4