Cover Page - USD ($)	12 Months Ended
	Jun. 30, 2019	Aug. 30, 2019	Dec. 31, 2018
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	001-34630
Entity Registrant Name	Aspen Technology, Inc
Entity Central Index Key	0000929940
Amendment Flag	false
Current Fiscal Year End Date	--06-30
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-2739697
Entity Address, Address Line One	20 Crosby Drive
Entity Address, City or Town	Bedford
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01730
City Area Code	781
Local Phone Number	221-6400
Title of 12(b) Security	Common stock, $0.10 par value per share
Trading Symbol	AZPN
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 5,131,947,302
Common stock held by non-affiliates			62,447,643
Share price as of December 31, 2018			$ 82.18
Entity Common Stock, Shares Outstanding		68,367,624
Documents Incorporated by Reference [Text Block]	Portions of the registrant's Proxy Statement related to its 2019 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission pursuant to Regulation 14A not later than 120 days after the end of the fiscal year covered by this Form 10-K are incorporated by reference in Part III, Items 10-14 of this Form 10-K.