INCOME TAXES - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning of year	$ 18.0	$ 13.8	$ 20.7
Gross increase – tax positions in prior period	84.4	4.1	1.0
Gross decrease – tax positions in prior period	(2.9)	(0.2)	(4.4)
Gross increase – tax positions in current period	1.7	1.2	2.4
Settlements	0.0	(0.2)	(1.6)
Lapse of statutes of limitations	(0.3)	(0.7)	(4.3)
Unrecognized tax benefits, end of year	$ 100.9	$ 18.0	$ 13.8