Stock-Based Compensation - Schedule of Share-Based Payment Arrangement, Cost by Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	$ 271	$ 144	$ 224
Income tax benefits recognized	28	19	27
Discontinued Operations
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	21	19	27
Continuing Operations
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	250	125	197
Performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	165	89	203
Restricted stock and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	24	23	21
AspenTech stock-based compensation plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	$ 82	$ 32	$ 0