Retirement Benefits - Schedule of Allocation of Plan Assets (Details) - USD ($) $ in Millions | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021 |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | $ 2,457.4 | $ 2,903.9 | |
Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 67.6 | 58.7 | $ 111.8 |
U.S. Plans | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 1,618.8 | 2,091.3 | |
U.S. Plans | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 1,607.1 | 2,073.3 | |
U.S. Plans | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 637.8 | 813.9 | |
U.S. Plans | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 969.3 | 1,259.4 | |
U.S. Plans | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Cash and cash equivalents | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 3.2 | 3.1 | |
U.S. Plans | Cash and cash equivalents | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 3.2 | 3.1 | |
U.S. Plans | Cash and cash equivalents | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Cash and cash equivalents | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Mutual funds | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 40.5 | 53.1 | |
U.S. Plans | Mutual funds | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 40.5 | 53.1 | |
U.S. Plans | Mutual funds | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Mutual funds | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Preferred and common stock | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 381.8 | 532.9 | |
U.S. Plans | Preferred and common stock | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 381.8 | 532.9 | |
U.S. Plans | Preferred and common stock | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Preferred and common stock | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Common collective trusts | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 447.4 | 621.1 | |
U.S. Plans | Common collective trusts | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Common collective trusts | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 447.4 | 621.1 | |
U.S. Plans | Common collective trusts | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Preferred and corporate debt | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 387.2 | 453.1 | |
U.S. Plans | Preferred and corporate debt | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Preferred and corporate debt | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 387.2 | 453.1 | |
U.S. Plans | Preferred and corporate debt | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Government securities | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 242.5 | 266.4 | |
U.S. Plans | Government securities | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 212.3 | 224.8 | |
U.S. Plans | Government securities | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 30.2 | 41.6 | |
U.S. Plans | Government securities | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Common collective trusts | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 104.5 | 143.6 | |
U.S. Plans | Common collective trusts | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Common collective trusts | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 104.5 | 143.6 | |
U.S. Plans | Common collective trusts | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
U.S. Plans | Insurance contracts | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | | 0 | 0.9 |
U.S. Plans | Private equity and alternative equity | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 11.7 | 18 | |
Non-U.S. Plans | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 838.6 | 812.6 | |
Non-U.S. Plans | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 819.9 | 796.3 | |
Non-U.S. Plans | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 162.5 | 157.8 | |
Non-U.S. Plans | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 589.8 | 579.8 | |
Non-U.S. Plans | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 67.6 | 58.7 | |
Non-U.S. Plans | Cash and cash equivalents | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 7 | 13.3 | |
Non-U.S. Plans | Cash and cash equivalents | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 7 | 13.3 | |
Non-U.S. Plans | Cash and cash equivalents | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Cash and cash equivalents | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Preferred and common stock | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 154.7 | 143.2 | |
Non-U.S. Plans | Preferred and common stock | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 154.7 | 143.2 | |
Non-U.S. Plans | Preferred and common stock | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Preferred and common stock | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Common collective trusts | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 209.7 | 185.1 | |
Non-U.S. Plans | Common collective trusts | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Common collective trusts | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 209.7 | 185.1 | |
Non-U.S. Plans | Common collective trusts | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Preferred and corporate debt | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 30.3 | 39.7 | |
Non-U.S. Plans | Preferred and corporate debt | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Preferred and corporate debt | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 30.3 | 39.7 | |
Non-U.S. Plans | Preferred and corporate debt | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Government securities | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0.8 | 1.3 | |
Non-U.S. Plans | Government securities | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0.8 | 1.3 | |
Non-U.S. Plans | Government securities | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Government securities | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Common collective trusts | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 294.5 | 291.3 | |
Non-U.S. Plans | Common collective trusts | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Common collective trusts | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 294.5 | 291.3 | |
Non-U.S. Plans | Common collective trusts | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Real estate funds | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 55.3 | 63.7 | |
Non-U.S. Plans | Real estate funds | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Real estate funds | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 55.3 | 63.7 | |
Non-U.S. Plans | Real estate funds | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Real estate funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 18.7 | 16.3 | |
Non-U.S. Plans | Insurance contracts | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 65.2 | 54.9 | |
Non-U.S. Plans | Insurance contracts | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Insurance contracts | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Insurance contracts | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 65.2 | 54.9 | 106.2 |
Non-U.S. Plans | Other | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 2.4 | 3.8 | |
Non-U.S. Plans | Other | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Other | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | 0 | 0 | |
Non-U.S. Plans | Other | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan fair value of plan assets | $ 2.4 | $ 3.8 | $ 4.7 |