Guarantor and Non-Guarantor Subsidiaries Financial Information - Consolidating Statement of Operations Unaudited (Detail) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Condensed Income Statements, Captions [Line Items]
Revenue		$ 1,256	$ 1,203
Costs and expenses:
Cost of revenue		(665)	(626)
Selling, general and administrative expenses	[1]	(379)	(376)
Amortization of intangible assets		(47)	(54)
Total costs and expenses		(1,091)	(1,056)
Operating income		165	147
Loss on extinguishment of debt		0	(3)
Interest (expense) income, net		(33)	(36)
Equity gains from equity method investments		0	0
Other income (expense), net		(5)	28
Income before income taxes		127	136
Income tax expense		(5)	(50)
Net income		122	86
Less: Income attributable to noncontrolling interest		(2)	0
Net income attributable to Warner Music Group Corp.		120	86
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenue		574	481
Costs and expenses:
Cost of revenue		(307)	(223)
Selling, general and administrative expenses		(177)	(189)
Amortization of intangible assets		(22)	(25)
Total costs and expenses		(506)	(437)
Operating income		68	44
Loss on extinguishment of debt			0
Interest (expense) income, net		0	1
Equity gains from equity method investments		86	109
Other income (expense), net		1	19
Income before income taxes		155	173
Income tax expense		(1)	(45)
Net income		154	128
Less: Income attributable to noncontrolling interest		0	0
Net income attributable to Warner Music Group Corp.		154	128
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenue		804	854
Costs and expenses:
Cost of revenue		(447)	(505)
Selling, general and administrative expenses		(235)	(217)
Amortization of intangible assets		(25)	(29)
Total costs and expenses		(707)	(751)
Operating income		97	103
Loss on extinguishment of debt			0
Interest (expense) income, net		(2)	(6)
Equity gains from equity method investments		0	0
Other income (expense), net		(8)	11
Income before income taxes		87	108
Income tax expense		(23)	(24)
Net income		64	84
Less: Income attributable to noncontrolling interest		(2)	0
Net income attributable to Warner Music Group Corp.		62	84
Reportable Legal Entities | Warner Music Group Corp.
Condensed Income Statements, Captions [Line Items]
Revenue		0	0
Costs and expenses:
Cost of revenue		0	0
Selling, general and administrative expenses		0	0
Amortization of intangible assets		0	0
Total costs and expenses		0	0
Operating income		0	0
Loss on extinguishment of debt			0
Interest (expense) income, net		0	0
Equity gains from equity method investments		120	86
Other income (expense), net		0	0
Income before income taxes		120	86
Income tax expense		0	0
Net income		120	86
Less: Income attributable to noncontrolling interest		0	0
Net income attributable to Warner Music Group Corp.		120	86
Reportable Legal Entities | WMG Acquisition Corp.
Condensed Income Statements, Captions [Line Items]
Revenue		0	0
Costs and expenses:
Cost of revenue		0	0
Selling, general and administrative expenses		0	0
Amortization of intangible assets		0	0
Total costs and expenses		0	0
Operating income		0	0
Loss on extinguishment of debt			(3)
Interest (expense) income, net		(31)	(31)
Equity gains from equity method investments		154	172
Other income (expense), net		2	(2)
Income before income taxes		125	136
Income tax expense		(5)	(50)
Net income		120	86
Less: Income attributable to noncontrolling interest		0	0
Net income attributable to Warner Music Group Corp.		120	86
Reportable Legal Entities | WMG Acquisition Corp. Consolidated
Condensed Income Statements, Captions [Line Items]
Revenue		1,256	1,203
Costs and expenses:
Cost of revenue		(665)	(626)
Selling, general and administrative expenses		(379)	(376)
Amortization of intangible assets		(47)	(54)
Total costs and expenses		(1,091)	(1,056)
Operating income		165	147
Loss on extinguishment of debt			(3)
Interest (expense) income, net		(33)	(36)
Equity gains from equity method investments		0	0
Other income (expense), net		(5)	28
Income before income taxes		127	136
Income tax expense		(5)	(50)
Net income		122	86
Less: Income attributable to noncontrolling interest		(2)	0
Net income attributable to Warner Music Group Corp.		120	86
Reportable Legal Entities | WMG Holdings Corp.
Condensed Income Statements, Captions [Line Items]
Revenue		0	0
Costs and expenses:
Cost of revenue		0	0
Selling, general and administrative expenses		0	0
Amortization of intangible assets		0	0
Total costs and expenses		0	0
Operating income		0	0
Loss on extinguishment of debt			0
Interest (expense) income, net		0	0
Equity gains from equity method investments		120	86
Other income (expense), net		0	0
Income before income taxes		120	86
Income tax expense		0	0
Net income		120	86
Less: Income attributable to noncontrolling interest		0	0
Net income attributable to Warner Music Group Corp.		120	86
Eliminations
Condensed Income Statements, Captions [Line Items]
Revenue		0	0
Costs and expenses:
Cost of revenue		0	0
Selling, general and administrative expenses		0	0
Amortization of intangible assets		0	0
Total costs and expenses		0	0
Operating income		0	0
Loss on extinguishment of debt			0
Interest (expense) income, net		0	0
Equity gains from equity method investments		(240)	(172)
Other income (expense), net		0	0
Income before income taxes		(240)	(172)
Income tax expense		0	0
Net income		(240)	(172)
Less: Income attributable to noncontrolling interest		0	0
Net income attributable to Warner Music Group Corp.		(240)	(172)
Eliminations | WMG Acquisition Corp.
Condensed Income Statements, Captions [Line Items]
Revenue		(122)	(132)
Costs and expenses:
Cost of revenue		89	102
Selling, general and administrative expenses		33	30
Amortization of intangible assets		0	0
Total costs and expenses		122	132
Operating income		0	0
Loss on extinguishment of debt			0
Interest (expense) income, net		0	0
Equity gains from equity method investments		(240)	(281)
Other income (expense), net		0	0
Income before income taxes		(240)	(281)
Income tax expense		24	69
Net income		(216)	(212)
Less: Income attributable to noncontrolling interest		0	0
Net income attributable to Warner Music Group Corp.		$ (216)	$ (212)

[1] (a) Includes depreciation expense:$(24) $(14)