Other Financial Data - Depreciation and Amortization Expense Components (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Business Acquisition [Line Items]
Depreciation expense	$ 287	$ 312	$ 330
Amortization of intangibles (includes $57, $108 and $196 reported in Cost of Sales in 2021, 2022 and 2023, respectively) (a)	678	444	334
Amortization of capitalized software	86	86	98
Total	1,051	842	762
Amortization if intangibles reported in Cost of Sales	196	108	57
Amortization of intangible assets	764	530	432
Heritage AspenTech
Business Acquisition [Line Items]
Amortization of intangible assets	$ 397	148
Amortization of intangibles - related restructuring		$ 14
Open Systems International, Inc. | Backlog
Business Acquisition [Line Items]
Amortization of intangible assets			$ 30