Stock-Based Compensation (AZPN Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
AspenTech [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received for stock options exercises	$ 14
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average exercise price per share, Beginning of year	$ 57.96
Average exercise price per share, Options granted	0
Average exercise price per share, Options exercised	57.21
Average exercise price per share, Options canceled	57.98
Average exercise price per share, End of year	58.10	$ 57.96
Average exercise price per share, Exercisable at year end	$ 58.10
Shares, Beginning of year	2,017,000
Shares, Options granted	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	315,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period	10,000
Shares, End of year	1,692,000	2,017,000
Shares, Exercisable at year end	1,692,000
Total intrinsic value of awards, End of year	$ 27
Total intrinsic value of awards, Exercisable at year end	$ 27
Average remaining life, Exercisable at year end	2 years 2 months 12 days
Average remaining life, End of year	2 years 2 months 12 days
Intrinsic value of options exercised	$ 11	$ 53	$ 47
Cash received for stock options exercises	$ 15	$ 114	$ 126
Stock Options [Member] | AspenTech [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average exercise price per share, Beginning of year	$ 0
Average exercise price per share, Options exercised	108.96
Average exercise price per share, Options canceled	149.16
Average exercise price per share, End of year	131.26	$ 0
Average exercise price per share, Exercisable at year end	101.76
Share-based Compensation Arrangement, Vested and expected to vest	$ 131.20
Shares, Beginning of year	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	(137,000)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period	(10,000)
Shares, End of year	1,256,000	0
Shares, Exercisable at year end	727,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	1,252,000
Total intrinsic value of awards, End of year	$ 134
Total intrinsic value of awards, Exercisable at year end	99
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	$ 134
Average remaining life, Exercisable at year end	5 years 7 months 6 days
Average remaining life, End of year	7 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	7 years
Expected dividend yield	0.00%
Risk-free interest rate	3.00%
Expected volatility rate	36.60%
Expected life of option	5 years 1 month 6 days
Weighted-average price of shares granted	$ 72.26
Intrinsic value of options exercised	$ 13
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Stock Options [Member] | AspenTech [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	7 years
Stock Options [Member] | AspenTech [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Stock Options [Member] | Replacement Awards Member | AspenTech [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average exercise price per share, Options granted	$ 101.44
Shares, Options granted	1,165,000
Stock Options [Member] | NonReplacement Awards Member | AspenTech [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average exercise price per share, Options granted	$ 204.27
Shares, Options granted	238,000