Guarantor and Non-Guarantor Subsidiaries Financial Information - Consolidating Statement of Comprehensive Income Unaudited (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Condensed Statement of Income Captions [Line Items]
Net income	$ 122	$ 86
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	7	(16)
Deferred gain (loss) on derivative financial instruments	3
Deferred (loss) gain on derivative		(6)
Other comprehensive income (loss), net of tax	10	(22)
Total comprehensive income	132	64
Less: Income attributable to noncontrolling interest	(2)	0
Comprehensive income attributable to Warner Music Group Corp.	130	64
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income	154	128
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	0	0
Deferred gain (loss) on derivative financial instruments	0
Deferred (loss) gain on derivative		0
Other comprehensive income (loss), net of tax	0	0
Total comprehensive income	154	128
Less: Income attributable to noncontrolling interest	0	0
Comprehensive income attributable to Warner Music Group Corp.	154	128
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income	64	84
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	(7)	16
Deferred gain (loss) on derivative financial instruments	3
Deferred (loss) gain on derivative		(2)
Other comprehensive income (loss), net of tax	(4)	14
Total comprehensive income	60	98
Less: Income attributable to noncontrolling interest	(2)	0
Comprehensive income attributable to Warner Music Group Corp.	58	98
Reportable Legal Entities | Warner Music Group Corp.
Condensed Statement of Income Captions [Line Items]
Net income	120	86
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	43	(16)
Deferred gain (loss) on derivative financial instruments	15
Deferred (loss) gain on derivative		(6)
Other comprehensive income (loss), net of tax	58	(22)
Total comprehensive income	178	64
Less: Income attributable to noncontrolling interest	0	0
Comprehensive income attributable to Warner Music Group Corp.	178	64
Reportable Legal Entities | WMG Acquisition Corp.
Condensed Statement of Income Captions [Line Items]
Net income	120	86
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	7	(16)
Deferred gain (loss) on derivative financial instruments	3
Deferred (loss) gain on derivative		(6)
Other comprehensive income (loss), net of tax	10	(22)
Total comprehensive income	130	64
Less: Income attributable to noncontrolling interest	0	0
Comprehensive income attributable to Warner Music Group Corp.	130	64
Reportable Legal Entities | WMG Acquisition Corp. Consolidated
Condensed Statement of Income Captions [Line Items]
Net income	122	86
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	7	(16)
Deferred gain (loss) on derivative financial instruments	3
Deferred (loss) gain on derivative		(6)
Other comprehensive income (loss), net of tax	10	(22)
Total comprehensive income	132	64
Less: Income attributable to noncontrolling interest	(2)	0
Comprehensive income attributable to Warner Music Group Corp.	130	64
Reportable Legal Entities | WMG Holdings Corp.
Condensed Statement of Income Captions [Line Items]
Net income	120	86
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	43	(16)
Deferred gain (loss) on derivative financial instruments	15
Deferred (loss) gain on derivative		(6)
Other comprehensive income (loss), net of tax	58	(22)
Total comprehensive income	178	64
Less: Income attributable to noncontrolling interest	0	0
Comprehensive income attributable to Warner Music Group Corp.	178	64
Eliminations
Condensed Statement of Income Captions [Line Items]
Net income	(240)	(172)
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	(86)	32
Deferred gain (loss) on derivative financial instruments	(30)
Deferred (loss) gain on derivative		12
Other comprehensive income (loss), net of tax	(116)	44
Total comprehensive income	(356)	(128)
Less: Income attributable to noncontrolling interest	0	0
Comprehensive income attributable to Warner Music Group Corp.	(356)	(128)
Eliminations | WMG Acquisition Corp.
Condensed Statement of Income Captions [Line Items]
Net income	(216)	(212)
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	7	(16)
Deferred gain (loss) on derivative financial instruments	(3)
Deferred (loss) gain on derivative		2
Other comprehensive income (loss), net of tax	4	(14)
Total comprehensive income	(212)	(226)
Less: Income attributable to noncontrolling interest	0	0
Comprehensive income attributable to Warner Music Group Corp.	$ (212)	$ (226)