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

+ 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

Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

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_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399

+ Details

Name:	us-gaap_DeferredFinanceCostsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the 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))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

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

- 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

- Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

Debt - Long-term Debt (Parenthetical) (Detail)					6 Months Ended	12 Months Ended
Debt - Long-term Debt (Parenthetical) (Detail)	Nov. 05, 2018	Oct. 12, 2018	Oct. 09, 2018 USD ($)	Mar. 14, 2018 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Mar. 31, 2019 EUR (€)	Sep. 30, 2018 EUR (€)	Mar. 31, 2018
Debt Instrument [Line Items]
Face or principal amount of debt instrument					$ 3,022,000,000	$ 2,851,000,000
Unamortized discount					4,000,000	4,000,000
Unamortized deferred financing costs					28,000,000	28,000,000
Acquisition Corp. \| Revolving Credit Facility
Debt Instrument [Line Items]
Commitments under revolving credit facility					180,000,000	180,000,000
Letters of credit outstanding					16,000,000	8,000,000
Revolving credit facility outstanding					$ 0	$ 0
Senior Term Loan Facility due 2023 \| Acquisition Corp.
Debt Instrument [Line Items]
Due date of senior secured notes					2023	2023
Face or principal amount of debt instrument					$ 1,326,000,000	$ 1,326,000,000
Unamortized discount					4,000,000	4,000,000
Unamortized deferred financing costs					$ 11,000,000	$ 12,000,000
5.000% Senior Secured Notes due 2023 \| Acquisition Corp.
Debt Instrument [Line Items]
Due date of senior secured notes					2023	2023
Interest rate					5.00%	5.00%	5.00%	5.00%
Face or principal amount of debt instrument					$ 300,000,000	$ 300,000,000
Unamortized deferred financing costs					$ 3,000,000	$ 3,000,000
4.125% Senior Secured Notes due 2024 \| Acquisition Corp.
Debt Instrument [Line Items]
Due date of senior secured notes		2024			2024	2024
Interest rate		4.125%	4.125%		4.125%	4.125%	4.125%	4.125%
Face or principal amount of debt instrument					$ 349,000,000	$ 402,000,000	€ 311,000,000	€ 345,000,000
Unamortized deferred financing costs					$ 3,000,000	$ 3,000,000
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]
Due date of senior secured notes			2024		2024	2024
Interest rate			4.875%		4.875%	4.875%	4.875%	4.875%
Face or principal amount of debt instrument			$ 30,000,000		$ 220,000,000	$ 250,000,000
Unamortized deferred financing costs					$ 3,000,000	$ 3,000,000
5.500% Senior Notes due 2026 \| Acquisition Corp.
Debt Instrument [Line Items]
Due date of senior secured notes				2026	2026	2026
Interest rate				5.50%	5.50%	5.50%	5.50%	5.50%
Face or principal amount of debt instrument				$ 325,000,000	$ 325,000,000	$ 325,000,000
Unamortized deferred financing costs					$ 4,000,000	$ 5,000,000
3.625% Senior Secured Notes due 2026 \| Acquisition Corp.
Debt Instrument [Line Items]
Due date of senior secured notes					2026	2026
Interest rate					3.625%	3.625%	3.625%	3.625%
Face or principal amount of debt instrument					$ 281,000,000		€ 250,000,000
Unamortized deferred financing costs					$ 3,000,000
5.625% Senior Secured Notes
Debt Instrument [Line Items]
Interest rate					5.625%		5.625%		5.625%
5.625% Senior Secured Notes \| Acquisition Corp.
Debt Instrument [Line Items]
Due date of senior secured notes	2022				2022	2022
Interest rate	5.625%				5.625%	5.625%	5.625%	5.625%
Face or principal amount of debt instrument					$ 221,000,000	$ 248,000,000
Unamortized deferred financing costs					$ 1,000,000	$ 2,000,000