CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2022	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 24.2	$ 173.9	$ 508.9	$ 321.5
Other comprehensive income (loss), net of tax:
Employee pension and postretirement benefits	8.6	56.7	61.7	(26.5)
Currency translation adjustments	(6.9)	(26.4)	3.8	30.4
Change in fair value of derivative instruments	0.7	6.0	1.9	(0.7)
Total other comprehensive income (loss), net of tax	2.4	36.3	67.4	3.2
Comprehensive income	$ 26.6	$ 210.2	$ 576.3	$ 324.7