Employee Benefit Plans - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ 2,400,000	$ 41,600,000	$ (43,900,000)
Accumulated benefit obligations	1,600,000,000	1,500,000,000
Contribution plan expense	14,100,000	12,500,000	15,900,000
Reserves for incentive plans	15,800,000	16,400,000
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	(140,000,000.0)	52,700,000
Accumulated benefit obligations	1,565,700,000	1,478,100,000	$ 1,585,200,000
Employer contributions	14,200,000	17,800,000
Expected future contribution	7,100,000
Pension benefits | United States
Defined Benefit Plan Disclosure [Line Items]
Expected future contribution	0
Other various benefit plans
Defined Benefit Plan Disclosure [Line Items]
Noncurrent postemployment benefits liability	$ 600,000	$ 1,000,000
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations	90.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations	10.00%