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Goodwill and Intangible Assets - Changes to the Carrying Amount of Goodwill by Segment (Details) - USD ($)	3 Months Ended
	Mar. 31, 2023	Sep. 30, 2022
Goodwill [Line Items]
Goodwill impairment		$ 0
Goodwill [Roll Forward]
Beginning balance	$ 2,930,211,000
Foreign currency translation impact	(270,000)
Ending balance	2,929,941,000
Goodwill, accumulated impairment losses	0
Research
Goodwill [Roll Forward]
Beginning balance	2,651,193,000
Foreign currency translation impact	(390,000)
Ending balance	2,650,803,000
Conferences
Goodwill [Roll Forward]
Beginning balance	183,951,000
Foreign currency translation impact	1,000
Ending balance	183,952,000
Consulting
Goodwill [Roll Forward]
Beginning balance	95,067,000
Foreign currency translation impact	119,000
Ending balance	$ 95,186,000

X

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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