Goodwill and Acquired Intangible Assets - Schedule of Changes in Goodwill by Reportable Segment (Details) - USD ($) $ in Thousands		12 Months Ended
	Apr. 29, 2022	Sep. 30, 2022	Sep. 30, 2021
Goodwill [Line Items]
Balance, beginning of period		$ 2,191,887	$ 1,625,786
Foreign currency translation adjustments		(46,903)	1,900
Balance, end of period		2,353,654	2,191,887
Divestiture of business
Goodwill [Line Items]
Goodwill, acquired		32,992
Intland Software
Goodwill [Line Items]
Goodwill, acquired	$ 240,900	240,971
Other Acquisitions
Goodwill [Line Items]
Goodwill, acquired		691	581
Arena Acquisition
Goodwill [Line Items]
Goodwill, acquired			563,620
Software Products
Goodwill [Line Items]
Balance, beginning of period		2,148,968	1,583,316
Foreign currency translation adjustments		(46,611)	1,851
Balance, end of period		2,344,019	2,148,968
Software Products | Divestiture of business
Goodwill [Line Items]
Goodwill, acquired		0
Software Products | Intland Software
Goodwill [Line Items]
Goodwill, acquired		240,971
Software Products | Other Acquisitions
Goodwill [Line Items]
Goodwill, acquired		691	181
Software Products | Arena Acquisition
Goodwill [Line Items]
Goodwill, acquired			563,620
Professional Services
Goodwill [Line Items]
Balance, beginning of period		42,919	42,470
Foreign currency translation adjustments		(292)	49
Balance, end of period		9,635	42,919
Professional Services | Divestiture of business
Goodwill [Line Items]
Goodwill, acquired		(32,992)
Professional Services | Intland Software
Goodwill [Line Items]
Goodwill, acquired		0
Professional Services | Other Acquisitions
Goodwill [Line Items]
Goodwill, acquired		$ 0	400
Professional Services | Arena Acquisition
Goodwill [Line Items]
Goodwill, acquired			$ 0