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=119993939&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=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

The net amount of nonoperating interest income (expense).

+ References

No definition available.

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24072-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in remainder of current fiscal year.

+ References

+ Details

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

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt - Additional Information (Detail)	3 Months Ended
Debt - Additional Information (Detail)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 EUR (€)	Nov. 02, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 EUR (€)	Aug. 12, 2020
Debt Instrument [Line Items]
Interest expense, net	$ 31,000,000	$ 33,000,000
Weighted-average interest rate of total debt	3.70%	4.20%	3.70%		3.70%	3.70%
Acquisition Corp.
Debt Instrument [Line Items]
Face or principal amount of debt instrument	$ 3,419,000,000				$ 3,127,000,000
3.625% Senior Secured Notes due 2026 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate	3.625%		3.625%
Face or principal amount of debt instrument	$ 543,000,000		€ 445,000,000		519,000,000	€ 445,000,000
5.500% Senior Notes due 2026 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate	5.50%		5.50%
Face or principal amount of debt instrument	$ 325,000,000				325,000,000
2.750% Senior Secured Notes due 2028 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate	2.75%		2.75%
Face or principal amount of debt instrument	$ 396,000,000		€ 325,000,000		379,000,000	€ 325,000,000
3.875% Senior Secured Notes due 2030 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate	3.875%		3.875%
Face or principal amount of debt instrument	$ 535,000,000				535,000,000
3.000% Senior Secured Notes due 2031
Debt Instrument [Line Items]
Interest rate	3.00%	3.00%	3.00%
3.000% Senior Secured Notes due 2031 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate	3.00%		3.00%	3.00%			3.00%
Face or principal amount of debt instrument	$ 800,000,000			$ 250,000,000	$ 550,000,000
Senior Notes
Debt Instrument [Line Items]
Scheduled maturities of long-term debt in 2021	0
Scheduled maturities of long-term debt in 2022	0
Scheduled maturities of long-term debt in 2023	0
Scheduled maturities of long-term debt in 2024	0
Scheduled maturities of long-term debt, 2025	0
Scheduled maturities of long-term debt, 2026	868,000,000
Scheduled maturities of long-term debt, thereafter	$ 1,731,000,000
Senior Notes \| 2.750% Senior Secured Notes due 2028 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate	2.75%		2.75%
Senior Notes \| 3.875% Senior Secured Notes due 2030 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate	3.875%		3.875%
Senior Notes \| 3.000% Senior Secured Notes due 2031 \| Acquisition Corp.
Debt Instrument [Line Items]
Interest rate	3.00%		3.00%