Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common stockholders' equity	Common stock	Additional paid-in-capital	Additional paid-in-capital AspenTech purchases of common stock	Retained earnings	Accumulated other comprehensive income (loss)	Treasury stock	Noncontrolling interests in subsidiaries	Noncontrolling interests in subsidiaries AspenTech purchases of common stock
Stockholders' equity, beginning balance at Sep. 30, 2023			$ 477	$ 62		$ 40,070	$ (1,253)	$ (18,667)	$ 5,909
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock plans				170
AspenTech purchases of common stock					$ (74)
Purchase of noncontrolling interest				0						$ 0
Settlement of AspenTech share awards				0
Reclass negative APIC to retained earnings				0		0
Purchases								(175)		(55)
Net earnings common stockholders	$ 643					643
Dividends paid (per share: $0.525, $0.5275, $1.050 and $1.055, respectively)						(605)			0
Foreign currency translation	180						178
Pension and postretirement	(24)						(24)
Cash flow hedges	2						2
Issued under stock plans								96
Net earnings (loss)									(8)
Stock plans									33
Other comprehensive income	158								2
Stockholders' equity, ending balance at Mar. 31, 2024	26,781	$ 20,900	477	158		40,108	(1,097)	(18,746)	5,881
Stockholders' equity, beginning balance at Dec. 31, 2023			477	140		39,910	(1,090)	(18,763)	5,881
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock plans				51
AspenTech purchases of common stock					(33)
Purchase of noncontrolling interest				0						0
Settlement of AspenTech share awards				0
Reclass negative APIC to retained earnings				0		0
Purchases								0		(24)
Net earnings common stockholders	501					501
Dividends paid (per share: $0.525, $0.5275, $1.050 and $1.055, respectively)						(303)			0
Foreign currency translation	6						6
Pension and postretirement	(12)						(12)
Cash flow hedges	(1)						(1)
Issued under stock plans								17
Net earnings (loss)									2
Stock plans									22
Other comprehensive income	(7)								0
Stockholders' equity, ending balance at Mar. 31, 2024	26,781	20,900	477	158		40,108	(1,097)	(18,746)	5,881
Stockholders' equity, beginning balance at Sep. 30, 2024	27,509		477	169		40,830	(868)	(18,972)	5,873
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock plans				(14)
AspenTech purchases of common stock					0
Purchase of noncontrolling interest				(1,400)						(5,832)
Settlement of AspenTech share awards				(76)
Reclass negative APIC to retained earnings				1,321		(1,321)
Purchases								(1,135)		0
Net earnings common stockholders	1,070					1,070
Dividends paid (per share: $0.525, $0.5275, $1.050 and $1.055, respectively)						(602)			(1)
Foreign currency translation	(303)						(298)
Pension and postretirement	6						6
Cash flow hedges	10						10
Issued under stock plans								52
Net earnings (loss)									(48)
Stock plans									30
Other comprehensive income	(287)								(5)
Stockholders' equity, ending balance at Mar. 31, 2025	19,266	19,249	477	0		39,977	(1,150)	(20,055)	17
Stockholders' equity, beginning balance at Dec. 31, 2024			477	113		41,112	(1,340)	(19,872)	5,889
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock plans				42
AspenTech purchases of common stock					$ 0
Purchase of noncontrolling interest				(1,400)						(5,832)
Settlement of AspenTech share awards				(76)
Reclass negative APIC to retained earnings				1,321		(1,321)
Purchases								(189)		$ 0
Net earnings common stockholders	485					485
Dividends paid (per share: $0.525, $0.5275, $1.050 and $1.055, respectively)						(299)			(1)
Foreign currency translation	189						187
Pension and postretirement	3						3
Cash flow hedges	0						0
Issued under stock plans								6
Net earnings (loss)									(55)
Stock plans									14
Other comprehensive income	192								2
Stockholders' equity, ending balance at Mar. 31, 2025	$ 19,266	$ 19,249	$ 477	$ 0		$ 39,977	$ (1,150)	$ (20,055)	$ 17