Retirement Benefits - Schedule of Allocation of Plan Assets (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	$ 2,810.0	$ 2,779.0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	74.0	74.0	$ 68.0
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	1,821.0	1,800.0
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	1,815.0	1,790.0
U.S. Plans \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	772.0	688.0
U.S. Plans \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	1,043.0	1,102.0
U.S. Plans \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	0.0	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	88.0	2.0
U.S. Plans \| Cash and cash equivalents \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	88.0	2.0
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	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	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	419.0	403.0
U.S. Plans \| Preferred and common stock \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	419.0	403.0
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	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	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	415.0	524.0
U.S. Plans \| Common collective trusts \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	0.0	0.0
U.S. Plans \| Common collective trusts \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	415.0	524.0
U.S. Plans \| Common collective trusts \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	0.0	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	478.0	431.0
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	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	478.0	431.0
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	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	295.0	314.0
U.S. Plans \| Government securities \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	265.0	283.0
U.S. Plans \| Government securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	30.0	31.0
U.S. Plans \| Government securities \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	0.0	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	120.0	116.0
U.S. Plans \| Common collective trusts \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	0.0	0.0
U.S. Plans \| Common collective trusts \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	120.0	116.0
U.S. Plans \| Common collective trusts \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	0.0	0.0
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	6.0	10.0
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	989.0	979.0
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	967.0	958.0
Non-U.S. Plans \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	209.0	199.0
Non-U.S. Plans \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	684.0	685.0
Non-U.S. Plans \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	74.0	74.0
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	8.0	6.0
Non-U.S. Plans \| Cash and cash equivalents \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	8.0	6.0
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	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	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	200.0	192.0
Non-U.S. Plans \| Preferred and common stock \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	200.0	192.0
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	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	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	218.0	218.0
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	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	218.0	218.0
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	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	79.0	80.0
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	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	79.0	80.0
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	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	1.0	1.0
Non-U.S. Plans \| Government securities \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	1.0	1.0
Non-U.S. Plans \| Government securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	0.0	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	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	327.0	333.0
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	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	327.0	333.0
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	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	60.0	54.0
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	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	60.0	54.0
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	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	23.0	21.0
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	73.0	72.0
Non-U.S. Plans \| Insurance contracts \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	0.0	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	0.0
Non-U.S. Plans \| Insurance contracts \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	73.0	72.0	65.0
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	1.0	2.0
Non-U.S. Plans \| Other \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	0.0	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	0.0
Non-U.S. Plans \| Other \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	$ 1.0	$ 2.0	$ 3.0

ROCKWELL AUTOMATION, INC 10-K