Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12355-112629

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12317-112629

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfSeniorDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Debt instrument, redemption price.

+ References

No definition available.

+ Details

Name:	wmg_DebtInstrumentRedemptionPrice
Namespace Prefix:	wmg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt instrument remaining outstanding amount.

+ References

No definition available.

+ Details

Name:	wmg_DebtInstrumentRemainingOutstandingAmount
Namespace Prefix:	wmg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=wmg_FourPointOneTwoFivePercentSeniorSecuredNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=wmg_AcquisitionCorpIssuerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=wmg_ThreePointSixTwoFivePercentSeniorSecuredNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt - Partial Redemption of 4.125% Senior Secured Notes (Details) € in Thousands, $ in Millions					12 Months Ended
	Jun. 30, 2020 USD ($)	Oct. 12, 2018 USD ($)	Oct. 12, 2018 EUR (€)	Oct. 09, 2018 EUR (€)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2020 EUR (€)	Jun. 29, 2020	Apr. 30, 2019
Debt Instrument [Line Items]
Redemptions of senior notes \| $					$ 0	$ 0	$ 635
Gain (loss) on extinguishment of debt \| $					$ (34)	$ (7)	$ (31)
4.125% Senior Secured Notes due 2024
Debt Instrument [Line Items]
Interest rate					4.125%	4.125%	4.125%
4.125% Senior Secured Notes due 2024 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate			4.125%	4.125%	4.125%			4.125%	4.125%
Redemptions of senior notes \| €			€ 34,500	€ 34,500
Senior notes redemption price \| €			€ 36,170
Redemption price, percentage of principal amount redeemed	103.094%	103.00%	103.00%
Debt instrument remaining outstanding amount \| €			€ 311,000					€ 322,000
Gain (loss) on extinguishment of debt \| $	$ (14)	$ (2)
3.625% Senior Secured Notes
Debt Instrument [Line Items]
Interest rate					3.625%	3.625%	3.625%
3.625% Senior Secured Notes \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate			3.625%	3.625%	3.625%					3.625%