Employee Benefit Plans - Schedule of Changes in The Benefit Obligations and Plan Assets, The Funded Status of The Plans and The Amounts Recognized in The Balance Sheet (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 601.1	$ 542.8
Change in projected benefit obligation
Benefit obligation at the beginning of the period	546.5	455.8
Service cost	10.1	9.1	$ 10.5
Interest cost	17.1	18.7	17.9
Actuarial loss (gain)	44.0	77.4
Participant contributions		0.1
Plan amendments	9.8	0.2
Curtailments		1.2
Benefits paid	(15.8)	(14.1)
Currency translation adjustments	1.9	(1.9)
Benefit obligation at the end of the period	613.6	546.5	455.8
Change in plan assets
Fair value of plan assets at the beginning of the period	408.9	384.2
Actual return on plan assets	35.4	33.9
Company contributions	11.4	8.8
Participant contributions		0.1
Expenses paid	(4.3)	(2.2)
Benefits paid	(15.8)	(14.1)
Currency translation adjustments	1.7	(1.8)
Fair value of plan assets at the end of the period	437.3	408.9	384.2
Funded status of plan - underfunded at September 30	(176.3)	(137.6)
Recognized in consolidated balance sheet at September 30
Accrued benefit liability (current liability)	(1.9)	(1.8)
Accrued benefit liability (long-term liability)	(174.4)	(135.8)
Total	(176.3)	(137.6)
Postretirement Health and Other
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	53.3	51.4
Change in projected benefit obligation
Benefit obligation at the beginning of the period	51.4	46.6
Service cost	3.5	3.1	3.7
Interest cost	1.6	1.9	1.8
Actuarial loss (gain)	5.4	1.4
Plan amendments	(6.5)
Benefits paid	(2.1)	(1.6)
Benefit obligation at the end of the period	53.3	51.4	$ 46.6
Change in plan assets
Company contributions	2.1	1.6
Benefits paid	(2.1)	(1.6)
Funded status of plan - underfunded at September 30	(53.3)	(51.4)
Recognized in consolidated balance sheet at September 30
Accrued benefit liability (current liability)	(2.5)	(1.2)
Accrued benefit liability (long-term liability)	(50.8)	(50.2)
Total	$ (53.3)	$ (51.4)