STOCK-BASED COMPENSATION - Schedule of Share-Based Payment Arrangement, Cost by Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	$ 260	$ 271	$ 144
Income tax benefits recognized	32	28	19
Discontinued Operations
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	0	21	19
Continuing Operations
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	260	250	125
Performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	90	165	89
Restricted stock and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	115	24	23
AspenTech stock-based compensation plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock compensation expense	$ 55	$ 82	$ 32