Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

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=6877327&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

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=114001942&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=114001942&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=109223946&loc=d3e3602-108585

+ Details

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

- Definition

Debt instrument maturity year.

+ References

No definition available.

+ Details

Name:	wmg_DebtInstrumentMaturityYear
Namespace Prefix:	wmg_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- 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_FourPointEightSevenFivePercentSeniorSecuredNotesDueInTwoThousandTwentyFourMember
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:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt - Open Market Purchase - Additional Information (Detail) - USD ($)		3 Months Ended	6 Months Ended		12 Months Ended
	Oct. 09, 2018	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Debt Instrument [Line Items]
Aggregate principal amount of debt instrument			$ 3,022,000,000		$ 2,851,000,000
Loss on extinguishment of debt		$ 23,000,000	$ 3,000,000	$ 24,000,000
4.875% Senior Secured Notes due 2024
Debt Instrument [Line Items]
Interest rate		4.875%	4.875%	4.875%
4.875% Senior Secured Notes due 2024 \| Acquisition Corp.
Debt Instrument [Line Items]
Aggregate principal amount of debt instrument	$ 30,000,000		$ 220,000,000		$ 250,000,000
Due date of senior secured notes	2024		2024		2024
Interest rate	4.875%		4.875%		4.875%
Debt instrument remaining outstanding amount	$ 220,000,000
4.875% Senior Secured Notes due 2024 \| Acquisition Corp. \| Maximum
Debt Instrument [Line Items]
Loss on extinguishment of debt	$ 1,000,000