Pension Benefit Obligations - Excess of Plan Assets (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
United States
Additional year-end information for pension plans with accumulated benefit obligations in excess of plan assets
Projected benefit obligation	$ 247.8	$ 265.1	$ 257.3
Accumulated benefit obligation	247.8	265.1	257.3
Fair values of plan assets	138.9	129.6	129.3
Expected employer contributions in next fiscal year	11.4
International
Additional year-end information for pension plans with accumulated benefit obligations in excess of plan assets
Projected benefit obligation	1,248.8	1,216.6	1,141.9
Accumulated benefit obligation	1,243.9	1,211.5	1,132.7
Fair values of plan assets	982.4	$ 898.5	$ 871.2
Expected employer contributions in next fiscal year	$ 24.8