RESTRUCTURING COSTS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2025
Restructuring [Line Items]
Expense	$ 21	$ 30	$ 32	$ 113
Other restructuring costs	6	3	8	7
AspenTech
Restructuring [Line Items]
Expense			1
National Instruments
Restructuring [Line Items]
Expense		10		36
Corporate and other
Restructuring [Line Items]
Expense	2	11	3	37
Corporate and other | AspenTech
Restructuring [Line Items]
Expense	$ 1		$ 1
Corporate and other | National Instruments
Restructuring [Line Items]
Expense		$ 11		$ 37
Forecast
Restructuring [Line Items]
Expected fiscal year restructuring expense					$ 140