For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8672-108599

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Number of customer.

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Segment Information - Narrative (Details)	12 Months Ended
Segment Information - Narrative (Details)	Sep. 30, 2021 segment customer	Sep. 30, 2020 customer	Sep. 30, 2019 customer
Segment Reporting Information [Line Items]
Number of fundamental operations	2
Number of reportable segments	2
Recorded Music And Music Publishing Segments \| Sales Revenue, Net \| Credit Concentration Risk
Segment Reporting Information [Line Items]
Number of customers \| customer	3	2	2
Recorded Music And Music Publishing Segments \| Sales Revenue, Net \| Credit Concentration Risk \| Spotify
Segment Reporting Information [Line Items]
Customer concentration percentage	18.00%	17.00%	14.00%
Recorded Music And Music Publishing Segments \| Sales Revenue, Net \| Credit Concentration Risk \| Apple
Segment Reporting Information [Line Items]
Customer concentration percentage	13.00%	14.00%	13.00%
Recorded Music And Music Publishing Segments \| Sales Revenue, Net \| Credit Concentration Risk \| YouTube
Segment Reporting Information [Line Items]
Customer concentration percentage	11.00%