Guarantor and Non-Guarantor Subsidiaries Financial Information - Consolidating Statement of Operations Unaudited (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Condensed Income Statements, Captions [Line Items]
Revenue		$ 1,058	$ 958	$ 3,351	$ 2,966
Costs and expenses:
Cost of revenue		(577)	(531)	(1,762)	(1,588)
Selling, general and administrative expenses	[1]	(372)	(343)	(1,102)	(1,013)
Amortization of intangible assets		(51)	(56)	(160)	(164)
Total costs and expenses		(1,000)	(930)	(3,024)	(2,765)
Operating income		58	28	327	201
Loss on extinguishment of debt		(4)	(7)	(7)	(31)
Interest (expense) income, net		(36)	(33)	(108)	(105)
Other income (expense), net		(16)	394	41	392
Income before income taxes		2	382	253	457
Income tax expense		12	(61)	(86)	(132)
Net income		14	321	167	325
Less: Income attributable to noncontrolling interest		(1)	(1)	(1)	(4)
Net income attributable to Warner Music Group Corp.		13	320	166	321
Reportable Legal Entities
Costs and expenses:
Net income		13	320	166	321
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenue		410	544	1,352	1,626
Costs and expenses:
Cost of revenue		(216)	(261)	(653)	(760)
Selling, general and administrative expenses		(198)	(252)	(573)	(731)
Amortization of intangible assets		(24)	(23)	(74)	(70)
Total costs and expenses		(438)	(536)	(1,300)	(1,561)
Operating income		(28)	8	52	65
Interest (expense) income, net			2	2	3
Equity gains (losses) from equity method investments		58	23	201	99
Other income (expense), net		37	(1)	107	8
Income before income taxes		67	32	362	175
Income tax expense		15	(62)	(79)	(131)
Net income		82	(30)	283	44
Less: Income attributable to noncontrolling interest					(1)
Net income attributable to Warner Music Group Corp.		82	(30)	283	43
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenue		760	533	2,286	1,703
Costs and expenses:
Cost of revenue		(442)	(346)	(1,338)	(1,066)
Selling, general and administrative expenses		(203)	(133)	(586)	(406)
Amortization of intangible assets		(27)	(33)	(86)	(94)
Total costs and expenses		(672)	(512)	(2,010)	(1,566)
Operating income		88	21	276	137
Loss on extinguishment of debt					(34)
Interest (expense) income, net		(6)	(8)	(18)	(21)
Other income (expense), net		(45)	19	(72)	8
Income before income taxes		37	32	186	124
Income tax expense		9	7	(41)	(21)
Net income		46	39	145	103
Less: Income attributable to noncontrolling interest		(1)	(1)	(1)	(3)
Net income attributable to Warner Music Group Corp.		45	38	144	100
Reportable Legal Entities | Warner Music Group Corp.
Costs and expenses:
Equity gains (losses) from equity method investments		13	320	166	321
Income before income taxes		13	320	166	321
Net income		13	320	166	321
Net income attributable to Warner Music Group Corp.		13	320	166	321
Reportable Legal Entities | WMG Acquisition Corp.
Costs and expenses:
Selling, general and administrative expenses		0		0
Total costs and expenses		0		0
Operating income		0		0
Loss on extinguishment of debt		(4)	(7)	(7)	(31)
Interest (expense) income, net		(30)	(27)	(92)	(87)
Equity gains (losses) from equity method investments		43	39	345	195
Other income (expense), net		(8)	376	6	376
Income before income taxes		1	381	252	453
Income tax expense		12	(61)	(86)	(132)
Net income		13	320	166	321
Net income attributable to Warner Music Group Corp.		13	320	166	321
Reportable Legal Entities | WMG Acquisition Corp. Consolidated
Condensed Income Statements, Captions [Line Items]
Revenue		1,058	958	3,351	2,966
Costs and expenses:
Cost of revenue		(577)	(531)	(1,762)	(1,588)
Selling, general and administrative expenses		(372)	(343)	(1,102)	(1,013)
Amortization of intangible assets		(51)	(56)	(160)	(164)
Total costs and expenses		(1,000)	(930)	(3,024)	(2,765)
Operating income		58	28	327	201
Loss on extinguishment of debt		(4)	(7)	(7)	(31)
Interest (expense) income, net		(36)	(33)	(108)	(105)
Other income (expense), net		(16)	394	41	392
Income before income taxes		2	382	253	457
Income tax expense		12	(61)	(86)	(132)
Net income		14	321	167	325
Less: Income attributable to noncontrolling interest		(1)	(1)	(1)	(4)
Net income attributable to Warner Music Group Corp.		13	320	166	321
Reportable Legal Entities | WMG Holdings Corp.
Costs and expenses:
Equity gains (losses) from equity method investments		13	320	166	321
Income before income taxes		13	320	166	321
Net income		13	320	166	321
Net income attributable to Warner Music Group Corp.		13	320	166	321
Eliminations
Costs and expenses:
Equity gains (losses) from equity method investments		(26)	(640)	(332)	(642)
Income before income taxes		(26)	(640)	(332)	(642)
Net income		(26)	(640)	(332)	(642)
Net income attributable to Warner Music Group Corp.		(26)	(640)	(332)	(642)
Eliminations | WMG Acquisition Corp.
Condensed Income Statements, Captions [Line Items]
Revenue		(112)	(119)	(287)	(363)
Costs and expenses:
Cost of revenue		81	76	229	238
Selling, general and administrative expenses		29	42	57	124
Total costs and expenses		110	118	286	362
Operating income		(2)	(1)	(1)	(1)
Equity gains (losses) from equity method investments		(101)	(62)	(546)	(294)
Income before income taxes		(103)	(63)	(547)	(295)
Income tax expense		(24)	55	120	152
Net income		(127)	(8)	(427)	(143)
Net income attributable to Warner Music Group Corp.		$ (127)	$ (8)	$ (427)	$ (143)

[1] (a) Includes depreciation expense of:$(15) $(15) $(43) $(41)