Retirement Benefits - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan Disclosure [Line Items]
Expense related to defined contribution savings plans	$ 76,900,000	$ 63,800,000	$ 58,500,000
Defined benefit plan, percentage of benefit obligation relating to domestic plan	70.00%
Recognized prior service credits	$ 123,500,000
Recognized prior service credits, net of tax	91,900,000
Recognized net actuarial losses	(2,100,000)
Recognized net actuarial losses, net of tax	$ (1,500,000)
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	$ 2,584,600,000	2,982,000,000
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to U.S. qualified pension plan	26,600,000	54,300,000
Recognized prior service credits	100,000	600,000	1,400,000
Recognized net actuarial losses	(2,600,000)	$ 59,400,000	$ 141,400,000
Estimated future payments, during next fiscal year	$ 26,600,000
Pension Benefits | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	6.10%	5.65%	3.10%
Pension Benefits | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.65%	4.35%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to U.S. qualified pension plan	$ 9,100,000	$ 7,900,000
Recognized prior service credits	0	(800,000)	$ (5,400,000)
Recognized net actuarial losses	500,000	$ 700,000	$ 1,100,000
Estimated future payments, during next fiscal year	$ 7,300,000
Other Postretirement Benefits | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	6.20%	5.70%
Other Postretirement Benefits | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.75%	5.10%
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%
Qualified Plan | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to U.S. qualified pension plan	$ 0	$ 0