Retirement Benefits - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Expense related to defined contribution savings plans	$ 91,700,000	$ 76,900,000	$ 63,800,000
Defined benefit plan, percentage of benefit obligation relating to domestic plan	70.00%
Recognized prior service credits	$ (100,000)
Recognized prior service credits, net of tax	0.0
Recognized net actuarial losses	(500,000)
Recognized net actuarial losses, net of tax	(400,000)
Defined benefit plan, net periodic benefit cost (credit) excluding service cost, statement of income or comprehensive income [extensible enumeration]		Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest
Defined benefit plan, accumulated benefit obligation	2,895,000,000	$ 2,584,600,000
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to U.S. qualified pension plan	0	0	0
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to U.S. qualified pension plan	27,300,000	26,600,000
Recognized prior service credits	0	100,000	600,000
Recognized net actuarial losses	(1,100,000)	$ (2,600,000)	59,400,000
Estimated future payments, during next fiscal year	$ 19,000,000.0
Pension Benefits | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.10%	6.10%
Pension Benefits | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.87%	4.65%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to U.S. qualified pension plan	$ 8,800,000	$ 9,100,000
Recognized prior service credits	0	0	(800,000)
Recognized net actuarial losses	1,600,000	$ 500,000	$ 700,000
Estimated future payments, during next fiscal year	$ 6,700,000
Other Postretirement Benefits | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.91%	6.20%
Other Postretirement Benefits | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.45%	5.75%
Minimum
Defined Benefit Plan Disclosure [Line Items]
Company contribution to defined contribution plan (percentage)	3.00%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Company contribution to defined contribution plan (percentage)	7.00%