Guarantor and Non-Guarantor Subsidiaries Financial Information - Consolidating Statement of Comprehensive Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Condensed Statement Of Income Captions [Line Items]
Net (loss) income	$ 149	$ 30	$ (88)
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	30	(44)	(59)
Minimum pension liability	7	(7)
Other comprehensive income (loss), net of tax	37	(51)	(59)
Total comprehensive income (loss)	186	(21)	(147)
Less: Income attributable to noncontrolling interest	(6)	(5)	(3)
Comprehensive income (loss) attributable to Warner Music Group Corp.	180	(26)	(150)
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Statement Of Income Captions [Line Items]
Net (loss) income	282	167	(42)
Other comprehensive income (loss), net of tax:
Deferred (loss) gain on derivative financial instruments	(1)	(1)
Other comprehensive income (loss), net of tax	(1)	(1)
Total comprehensive income (loss)	281	166	(42)
Less: Income attributable to noncontrolling interest	(1)	(1)	(1)
Comprehensive income (loss) attributable to Warner Music Group Corp.	280	165	(43)
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Statement Of Income Captions [Line Items]
Net (loss) income	59	54	(15)
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	(30)	(44)	(59)
Minimum pension liability	7	(7)
Other comprehensive income (loss), net of tax	(23)	(51)	(59)
Total comprehensive income (loss)	36	3	(74)
Less: Income attributable to noncontrolling interest	(5)	(4)	(2)
Comprehensive income (loss) attributable to Warner Music Group Corp.	31	(1)	(76)
Reportable Legal Entities | Warner Music Group Corp.
Condensed Statement Of Income Captions [Line Items]
Net (loss) income	143	25	(91)
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	32	(44)	(59)
Minimum pension liability	7	(7)
Other comprehensive income (loss), net of tax	39	(51)	(59)
Total comprehensive income (loss)	182	(26)	(150)
Comprehensive income (loss) attributable to Warner Music Group Corp.	182	(26)	(150)
Reportable Legal Entities | Acquisition Corp.
Condensed Statement Of Income Captions [Line Items]
Net (loss) income	143	53	(69)
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	30	(44)	(59)
Minimum pension liability	7	(7)
Other comprehensive income (loss), net of tax	37	(51)	(59)
Total comprehensive income (loss)	180	2	(128)
Comprehensive income (loss) attributable to Warner Music Group Corp.	180	2	(128)
Reportable Legal Entities | WMG Acquisition Corp. Consolidated
Condensed Statement Of Income Captions [Line Items]
Net (loss) income	149	58	(66)
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	30	(44)	(59)
Minimum pension liability	7	(7)
Other comprehensive income (loss), net of tax	37	(51)	(59)
Total comprehensive income (loss)	186	7	(125)
Less: Income attributable to noncontrolling interest	(6)	(5)	(3)
Comprehensive income (loss) attributable to Warner Music Group Corp.	180	2	(128)
Reportable Legal Entities | WMG Holdings Corp.
Condensed Statement Of Income Captions [Line Items]
Net (loss) income	143	25	(91)
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	32	(44)	(59)
Minimum pension liability	7	(7)
Other comprehensive income (loss), net of tax	39	(51)	(59)
Total comprehensive income (loss)	182	(26)	(150)
Comprehensive income (loss) attributable to Warner Music Group Corp.	182	(26)	(150)
Eliminations
Condensed Statement Of Income Captions [Line Items]
Net (loss) income	(286)	(78)	160
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	(64)	88	118
Minimum pension liability	(14)	14
Other comprehensive income (loss), net of tax	(78)	102	118
Total comprehensive income (loss)	(364)	24	278
Comprehensive income (loss) attributable to Warner Music Group Corp.	(364)	24	278
Eliminations | Acquisition Corp.
Condensed Statement Of Income Captions [Line Items]
Net (loss) income	(335)	(216)	60
Other comprehensive income (loss), net of tax:
Foreign currency adjustment	30	44	59
Minimum pension liability	(7)	7
Deferred (loss) gain on derivative financial instruments	1	1
Other comprehensive income (loss), net of tax	24	52	59
Total comprehensive income (loss)	(311)	(164)	119
Comprehensive income (loss) attributable to Warner Music Group Corp.	$ (311)	$ (164)	$ 119