The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Quarterly Financial Information - Quarterly Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Quarterly Financial Information [Line Items]
Revenues									$ 4,463	$ 4,475	$ 4,005
Costs and expenses:
Cost of revenue									(2,333)	(2,401)	(2,171)
Selling, general and administrative expenses									(2,169)	(1,510)	(1,411)
Amortization expense									(190)	(208)	(206)
Total costs and expenses									(4,692)	(4,119)	(3,788)
Operating (loss) income									(229)	356	217
Loss on extinguishment of debt									34	7	31
Interest expense, net									(127)	(142)	(138)
Other (expense) income									(57)	60	394
(Loss) income before income taxes									(447)	267	442
Income tax (expense) benefit									(23)	(9)	(130)
Net (loss) income									(470)	258	312
Less: Income attributable to noncontrolling interest									(5)	(2)	(5)
Net (loss) income attributable to Warner Music Group Corp.									(475)	256	307
Quarterly Financial Information
Quarterly Financial Information [Line Items]
Revenues	$ 1,126	$ 1,010	$ 1,071	$ 1,256	$ 1,124	$ 1,058	$ 1,090	$ 1,203
Costs and expenses:
Cost of revenue	(606)	(527)	(535)	(665)	(639)	(577)	(559)	(626)
Selling, general and administrative expenses	(383)	(869)	(538)	(379)	(408)	(372)	(354)	(376)
Amortization expense	(49)	(47)	(47)	(47)	(48)	(51)	(55)	(54)
Total costs and expenses	(1,038)	(1,443)	(1,120)	(1,091)	(1,095)	(1,000)	(968)	(1,056)
Operating (loss) income	88	(433)	(49)	165	29	58	122	147
Loss on extinguishment of debt	34	0	0	0	0	4	0	3
Interest expense, net	(29)	(32)	(33)	(33)	(34)	(36)	(36)	(36)
Other (expense) income	(45)	(3)	(4)	(5)	19	(16)	29	28
(Loss) income before income taxes	(20)	(468)	(86)	127	14	2	115	136
Income tax (expense) benefit	21	(51)	12	(5)	77	12	(48)	(50)
Net (loss) income	1	(519)	(74)	122	91	14	67	86
Less: Income attributable to noncontrolling interest	(2)	(1)	0	(2)	(1)	(1)	0	0
Net (loss) income attributable to Warner Music Group Corp.	$ (1)	$ (520)	$ (74)	$ 120	$ 90	$ 13	$ 67	$ 86
Common Class A
Costs and expenses:
Net (loss) income attributable to Warner Music Group Corp.									(21)	0	0
Common Class B
Costs and expenses:
Net (loss) income attributable to Warner Music Group Corp.									$ (454)	$ 256	$ 307