Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Operating Loss Carryforwards [Line Items]
Valuation allowance - increase	$ (35.0)	$ 20.1
Excess tax benefit from the exercise of stock options and lapses of restricted stock units	15.0	24.6	$ 13.4
Income tax payments, net of refunds	603.9	463.1	$ 244.4
Undistributed earnings of international subsidiaries	3,900.0
Permanently reinvested cumulative undistributed earnings	2,100.0
Unrecognized tax benefits, including interest and penalties	545.0	551.9
Unrecognized tax benefits, including interest and penalties, net of federal benefit	498.0	482.7
Unrecognized tax benefits that would impact effective tax rate	488.1	464.4
Unrecognized tax benefits, interest and penalties	43.9	$ 25.9
Reduction of unrecognized tax benefits reasonably possible	13.5
Federal
Operating Loss Carryforwards [Line Items]
Potential tax benefits from net operating loss carryforwards	106.3
Tax credit carryforwards	4.7
Foreign
Operating Loss Carryforwards [Line Items]
Potential tax benefits from net operating loss carryforwards	443.1
Foreign | Alternative minimum tax credit carryforwards
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	3.1
State
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 4.6