Pension Benefit Obligations - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Aggregate contributions to multiemployer plans	$ 2.7	$ 2.5
U.S.
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions in next fiscal year	$ 10.8
Weighted-average long-term rate of return on assets assumption (as percent)	6.25%	6.90%	7.00%
Aggregate contributions to multiemployer plans	$ 10.6	$ 11.9	$ 8.2
Int’l
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions in next fiscal year	$ 25.0
Weighted-average long-term rate of return on assets assumption (as percent)	5.51%	5.74%	6.04%
Aggregate contributions to multiemployer plans	$ 23.7	$ 25.1	$ 24.8
Pension Plan, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Applicable deferred income taxes, included in OCI arising from net prior service cost and net gain/loss	$ 1.1	$ 2.1	$ 3.1