Guarantor and Non-Guarantor Subsidiaries Financial Information - Consolidating Balance Sheet Unaudited (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Current assets:
Cash and equivalents	$ 462	$ 619
Accounts receivable, net	882	775
Inventories	65	74
Royalty advances expected to be recouped within one year	189	170
Prepaid and other current assets	58	53
Total current assets	1,656	1,691
Due from (to) parent companies	0	0
Investments in and advances to consolidated subsidiaries	0	0
Royalty advances expected to be recouped after one year	231	208
Property, plant and equipment, net	295	300
Operating lease right-of-use assets, net	289
Goodwill	1,768	1,761
Intangible assets subject to amortization, net	1,712	1,723
Intangible assets not subject to amortization	152	151
Deferred tax assets, net	59	38
Other assets	152	145
Total assets	6,314	6,017
Current liabilities:
Accounts payable	202	260
Accrued royalties	1,671	1,567
Accrued liabilities	549	492
Accrued interest	23	34
Operating lease liabilities, current	38
Deferred revenue	159	180
Other current liabilities	157	286
Total current liabilities	2,799	2,819
Long-term debt	2,988	2,974
Operating lease liabilities, noncurrent	321	0
Deferred tax liabilities, net	171	172
Other noncurrent liabilities	204	321
Total liabilities	6,483	6,286
Total Warner Music Group Corp. deficit	(190)	(289)
Noncontrolling interest	21	20
Total equity	(169)	(269)	$ (139)	$ (320)
Total liabilities and equity	6,314	6,017
Reportable Legal Entities | Guarantor Subsidiaries
Current assets:
Cash and equivalents	184	386
Accounts receivable, net	390	334
Inventories	13	11
Royalty advances expected to be recouped within one year	119	112
Prepaid and other current assets	15	12
Total current assets	721	855
Due from (to) parent companies	(659)	(531)
Investments in and advances to consolidated subsidiaries	2,710	2,567
Royalty advances expected to be recouped after one year	146	137
Property, plant and equipment, net	190	200
Operating lease right-of-use assets, net	211
Goodwill	1,370	1,370
Intangible assets subject to amortization, net	870	884
Intangible assets not subject to amortization	72	71
Deferred tax assets, net	51	30
Other assets	119	115
Total assets	5,801	5,698
Current liabilities:
Accounts payable	109	160
Accrued royalties	777	813
Accrued liabilities	303	266
Accrued interest	0	0
Operating lease liabilities, current	21
Deferred revenue	35	42
Other current liabilities	53	221
Total current liabilities	1,298	1,502
Long-term debt	0	0
Operating lease liabilities, noncurrent	259
Deferred tax liabilities, net	0	0
Other noncurrent liabilities	94	200
Total liabilities	1,651	1,702
Total Warner Music Group Corp. deficit	4,146	3,992
Noncontrolling interest	4	4
Total equity	4,150	3,996
Total liabilities and equity	5,801	5,698
Reportable Legal Entities | Non-Guarantor Subsidiaries
Current assets:
Cash and equivalents	278	233
Accounts receivable, net	492	441
Inventories	52	63
Royalty advances expected to be recouped within one year	70	58
Prepaid and other current assets	43	41
Total current assets	935	836
Due from (to) parent companies	184	73
Investments in and advances to consolidated subsidiaries	0	0
Royalty advances expected to be recouped after one year	85	71
Property, plant and equipment, net	105	100
Operating lease right-of-use assets, net	78
Goodwill	398	391
Intangible assets subject to amortization, net	842	839
Intangible assets not subject to amortization	80	80
Deferred tax assets, net	8	8
Other assets	24	23
Total assets	2,739	2,421
Current liabilities:
Accounts payable	93	100
Accrued royalties	894	750
Accrued liabilities	246	226
Accrued interest	0	0
Operating lease liabilities, current	17
Deferred revenue	124	138
Other current liabilities	104	65
Total current liabilities	1,478	1,279
Long-term debt	0	0
Operating lease liabilities, noncurrent	62
Deferred tax liabilities, net	171	172
Other noncurrent liabilities	99	107
Total liabilities	1,810	1,558
Total Warner Music Group Corp. deficit	912	847
Noncontrolling interest	17	16
Total equity	929	863
Total liabilities and equity	2,739	2,421
Reportable Legal Entities | Warner Music Group Corp.
Current assets:
Cash and equivalents	0	0
Accounts receivable, net	0	0
Inventories	0	0
Royalty advances expected to be recouped within one year	0	0
Prepaid and other current assets	0	0
Total current assets	0	0
Due from (to) parent companies	0	0
Investments in and advances to consolidated subsidiaries	805	878
Royalty advances expected to be recouped after one year	0	0
Property, plant and equipment, net	0	0
Operating lease right-of-use assets, net	0
Goodwill	0	0
Intangible assets subject to amortization, net	0	0
Intangible assets not subject to amortization	0	0
Deferred tax assets, net	0	0
Other assets	0	0
Total assets	805	878
Current liabilities:
Accounts payable	0	0
Accrued royalties	0	0
Accrued liabilities	0	0
Accrued interest	0	0
Operating lease liabilities, current	0
Deferred revenue	0	0
Other current liabilities	0	0
Total current liabilities	0	0
Long-term debt	0	0
Operating lease liabilities, noncurrent	0
Deferred tax liabilities, net	0	0
Other noncurrent liabilities	0	0
Total liabilities	0	0
Total Warner Music Group Corp. deficit	805	878
Noncontrolling interest	0	0
Total equity	805	878
Total liabilities and equity	805	878
Reportable Legal Entities | WMG Acquisition Corp.
Current assets:
Cash and equivalents	0	0
Accounts receivable, net	0	0
Inventories	0	0
Royalty advances expected to be recouped within one year	0	0
Prepaid and other current assets	0	0
Total current assets	0	0
Due from (to) parent companies	475	458
Investments in and advances to consolidated subsidiaries	2,348	2,272
Royalty advances expected to be recouped after one year	0	0
Property, plant and equipment, net	0	0
Operating lease right-of-use assets, net	0
Goodwill	0	0
Intangible assets subject to amortization, net	0	0
Intangible assets not subject to amortization	0	0
Deferred tax assets, net	0	0
Other assets	9	7
Total assets	2,832	2,737
Current liabilities:
Accounts payable	0	0
Accrued royalties	0	4
Accrued liabilities	0	0
Accrued interest	23	34
Operating lease liabilities, current	0
Deferred revenue	0	0
Other current liabilities	0	0
Total current liabilities	23	38
Long-term debt	2,988	2,974
Operating lease liabilities, noncurrent	0
Deferred tax liabilities, net	0	0
Other noncurrent liabilities	11	14
Total liabilities	3,022	3,026
Total Warner Music Group Corp. deficit	(190)	(289)
Noncontrolling interest	0	0
Total equity	(190)	(289)
Total liabilities and equity	2,832	2,737
Reportable Legal Entities | WMG Acquisition Corp. Consolidated
Current assets:
Cash and equivalents	462	619
Accounts receivable, net	882	775
Inventories	65	74
Royalty advances expected to be recouped within one year	189	170
Prepaid and other current assets	58	53
Total current assets	1,656	1,691
Due from (to) parent companies	0	0
Investments in and advances to consolidated subsidiaries	0	0
Royalty advances expected to be recouped after one year	231	208
Property, plant and equipment, net	295	300
Operating lease right-of-use assets, net	289
Goodwill	1,768	1,761
Intangible assets subject to amortization, net	1,712	1,723
Intangible assets not subject to amortization	152	151
Deferred tax assets, net	59	38
Other assets	152	145
Total assets	6,314	6,017
Current liabilities:
Accounts payable	202	260
Accrued royalties	1,671	1,567
Accrued liabilities	549	492
Accrued interest	23	34
Operating lease liabilities, current	38
Deferred revenue	159	180
Other current liabilities	157	286
Total current liabilities	2,799	2,819
Long-term debt	2,988	2,974
Operating lease liabilities, noncurrent	321
Deferred tax liabilities, net	171	172
Other noncurrent liabilities	204	321
Total liabilities	6,483	6,286
Total Warner Music Group Corp. deficit	(190)	(289)
Noncontrolling interest	21	20
Total equity	(169)	(269)
Total liabilities and equity	6,314	6,017
Reportable Legal Entities | WMG Holdings Corp.
Current assets:
Cash and equivalents	0	0
Accounts receivable, net	0	0
Inventories	0	0
Royalty advances expected to be recouped within one year	0	0
Prepaid and other current assets	0	0
Total current assets	0	0
Due from (to) parent companies	0	0
Investments in and advances to consolidated subsidiaries	805	878
Royalty advances expected to be recouped after one year	0	0
Property, plant and equipment, net	0	0
Operating lease right-of-use assets, net	0
Goodwill	0	0
Intangible assets subject to amortization, net	0	0
Intangible assets not subject to amortization	0	0
Deferred tax assets, net	0	0
Other assets	0	0
Total assets	805	878
Current liabilities:
Accounts payable	0	0
Accrued royalties	0	0
Accrued liabilities	0	0
Accrued interest	0	0
Operating lease liabilities, current	0
Deferred revenue	0	0
Other current liabilities	0	0
Total current liabilities	0	0
Long-term debt	0	0
Operating lease liabilities, noncurrent	0
Deferred tax liabilities, net	0	0
Other noncurrent liabilities	0	0
Total liabilities	0	0
Total Warner Music Group Corp. deficit	805	878
Noncontrolling interest	0	0
Total equity	805	878
Total liabilities and equity	805	878
Eliminations
Current assets:
Cash and equivalents	0	0
Accounts receivable, net	0	0
Inventories	0	0
Royalty advances expected to be recouped within one year	0	0
Prepaid and other current assets	0	0
Total current assets	0	0
Due from (to) parent companies	0	0
Investments in and advances to consolidated subsidiaries	(1,610)	(1,756)
Royalty advances expected to be recouped after one year	0	0
Property, plant and equipment, net	0	0
Operating lease right-of-use assets, net	0
Goodwill	0	0
Intangible assets subject to amortization, net	0	0
Intangible assets not subject to amortization	0	0
Deferred tax assets, net	0	0
Other assets	0	0
Total assets	(1,610)	(1,756)
Current liabilities:
Accounts payable	0	0
Accrued royalties	0	0
Accrued liabilities	0	0
Accrued interest	0	0
Operating lease liabilities, current	0
Deferred revenue	0	0
Other current liabilities	0	0
Total current liabilities	0	0
Long-term debt	0	0
Operating lease liabilities, noncurrent	0
Deferred tax liabilities, net	0	0
Other noncurrent liabilities	0	0
Total liabilities	0	0
Total Warner Music Group Corp. deficit	(1,610)	(1,756)
Noncontrolling interest	0	0
Total equity	(1,610)	(1,756)
Total liabilities and equity	(1,610)	(1,756)
Eliminations | WMG Acquisition Corp.
Current assets:
Cash and equivalents	0	0
Accounts receivable, net	0	0
Inventories	0	0
Royalty advances expected to be recouped within one year	0	0
Prepaid and other current assets	0	0
Total current assets	0	0
Due from (to) parent companies	0	0
Investments in and advances to consolidated subsidiaries	(5,058)	(4,839)
Royalty advances expected to be recouped after one year	0	0
Property, plant and equipment, net	0	0
Operating lease right-of-use assets, net	0
Goodwill	0	0
Intangible assets subject to amortization, net	0	0
Intangible assets not subject to amortization	0	0
Deferred tax assets, net	0	0
Other assets	0	0
Total assets	(5,058)	(4,839)
Current liabilities:
Accounts payable	0	0
Accrued royalties	0	0
Accrued liabilities	0	0
Accrued interest	0	0
Operating lease liabilities, current	0
Deferred revenue	0	0
Other current liabilities	0	0
Total current liabilities	0	0
Long-term debt	0	0
Operating lease liabilities, noncurrent	0
Deferred tax liabilities, net	0	0
Other noncurrent liabilities	0	0
Total liabilities	0	0
Total Warner Music Group Corp. deficit	(5,058)	(4,839)
Noncontrolling interest	0	0
Total equity	(5,058)	(4,839)
Total liabilities and equity	$ (5,058)	$ (4,839)