Guarantor and Non-Guarantor Subsidiaries Financial Information - Consolidating Statement of Cash Flows Unaudited (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net income	$ 14	$ 321	$ 167	$ 325
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			203	205
Unrealized gains on remeasurement of foreign denominated loans			(6)	(6)
Deferred income taxes			25	105
Loss on extinguishment of debt	4	7	7	31
Net gain on divestitures and investments			(27)	(385)
Non-cash interest expense			5	5
Equity-based compensation expense			28	52
Changes in operating assets and liabilities:
Accounts receivable, net			(50)	(43)
Inventories			12	(1)
Royalty advances			(107)	0
Accounts payable and accrued liabilities			(94)	(84)
Royalty payables			117	113
Accrued interest			(13)	(22)
Deferred revenue			(17)	0
Other balance sheet changes			(1)	(30)
Net cash provided by operating activities			249	265
Cash flows from investing activities
Acquisition of music publishing rights, net			(24)	(11)
Capital expenditures			(82)	(40)
Investments and acquisitions of businesses, net			(234)	(14)
Proceeds from the sale of investments			0	516
Net cash (used in) provided by investing activities			(340)	451
Cash flows from financing activities
Call premiums paid on and redemption deposit for early redemption of debt			(5)	(23)
Deferred financing costs paid			(7)	(12)
Distribution to noncontrolling interest holder			(3)	(3)
Dividends paid			(63)	(425)
Net cash provided by (used in) financing activities			119	(453)
Proceeds from supplement of Acquisition Corp. Senior Term Loan Facility			0	320
Effect of exchange rate changes on cash and equivalents			(1)	(5)
Net increase in cash and equivalents			27	258
Cash and equivalents at beginning of period			514	647
Cash and equivalents at end of period	541	905	541	905
3.625% Senior Secured Notes due 2026
Cash flows from financing activities
Proceeds from issuance of Acquisition Corp			514
4.125% Senior Secured Notes
Cash flows from financing activities
Repayment of Senior Secured Notes			(40)
4.875% Senior Secured Notes
Cash flows from financing activities
Repayment of Senior Secured Notes			(30)
5.625% Senior Secured Notes
Cash flows from financing activities
Repayment of Senior Secured Notes			(247)
5.50% Senior Notes
Cash flows from financing activities
Proceeds from issuance of Acquisition Corp			0	325
6.75% Senior Notes
Cash flows from financing activities
Repayment of and redemption deposit for Acquisition Corp. Senior Notes			0	(635)
Reportable Legal Entities
Cash flows from operating activities
Net income	13	320	166	321
Reportable Legal Entities | Guarantor Subsidiaries
Cash flows from operating activities
Net income	82	(30)	283	44
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			103	101
Unrealized gains on remeasurement of foreign denominated loans			(1)	(3)
Net gain on divestitures and investments			(25)	84
Equity-based compensation expense			28	52
Equity gains, including distributions			(201)	(99)
Changes in operating assets and liabilities:
Accounts receivable, net			11	(39)
Inventories			5	(5)
Royalty advances			(57)
Accounts payable and accrued liabilities			239	256
Royalty payables			(82)	32
Deferred revenue			(45)	30
Other balance sheet changes			54	82
Net cash provided by operating activities			312	535
Cash flows from investing activities
Acquisition of music publishing rights, net			(19)	(7)
Capital expenditures			(70)	(30)
Investments and acquisitions of businesses, net			(40)	(14)
Proceeds from the sale of investments				12
Net cash (used in) provided by investing activities			(129)	(39)
Cash flows from financing activities
Distribution to noncontrolling interest holder			0
Dividends paid			(63)	(397)
Change in due to (from) issuer			8	108
Net cash provided by (used in) financing activities			(55)	(289)
Net increase in cash and equivalents			128	207
Cash and equivalents at beginning of period			169	347
Cash and equivalents at end of period	297	554	297	554
Reportable Legal Entities | Non-Guarantor Subsidiaries
Cash flows from operating activities
Net income	46	39	145	103
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			100	104
Unrealized gains on remeasurement of foreign denominated loans				2
Deferred income taxes			25	105
Loss on extinguishment of debt				34
Net gain on divestitures and investments			(2)
Changes in operating assets and liabilities:
Accounts receivable, net			(61)	(4)
Inventories			7	4
Royalty advances			(50)
Accounts payable and accrued liabilities			(214)	(189)
Royalty payables			194	81
Deferred revenue			28	(30)
Other balance sheet changes			(58)	(109)
Net cash provided by operating activities			114	101
Cash flows from investing activities
Acquisition of music publishing rights, net			(5)	(4)
Capital expenditures			(12)	(10)
Investments and acquisitions of businesses, net			(194)
Net cash (used in) provided by investing activities			(211)	(14)
Cash flows from financing activities
Distribution to noncontrolling interest holder			(3)	(3)
Dividends paid				(28)
Net cash provided by (used in) financing activities			(3)	(31)
Effect of exchange rate changes on cash and equivalents			(1)	(5)
Net increase in cash and equivalents			(101)	51
Cash and equivalents at beginning of period			345	300
Cash and equivalents at end of period	244	351	244	351
Reportable Legal Entities | Warner Music Group Corp.
Cash flows from operating activities
Net income	13	320	166	321
Adjustments to reconcile net income to net cash provided by operating activities:
Equity gains, including distributions			(166)	(321)
Reportable Legal Entities | WMG Acquisition Corp.
Cash flows from operating activities
Net income	13	320	166	321
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized gains on remeasurement of foreign denominated loans			(5)	(5)
Loss on extinguishment of debt	4	7	7	31
Net gain on divestitures and investments				(503)
Non-cash interest expense			5	5
Equity gains, including distributions			(345)	(195)
Changes in operating assets and liabilities:
Royalty payables			5
Accrued interest			(13)	(22)
Other balance sheet changes			3	(3)
Net cash provided by operating activities			(177)	(371)
Cash flows from investing activities
Proceeds from the sale of investments				504
Advances from issuer			(8)	(108)
Net cash (used in) provided by investing activities			(8)	396
Cash flows from financing activities
Call premiums paid on and redemption deposit for early redemption of debt			(5)	(23)
Deferred financing costs paid			(7)	(12)
Net cash provided by (used in) financing activities			185	(25)
Proceeds from supplement of Acquisition Corp. Senior Term Loan Facility				320
Net increase in cash and equivalents			0
Cash and equivalents at end of period	0		0
Reportable Legal Entities | WMG Acquisition Corp. | 3.625% Senior Secured Notes due 2026
Cash flows from financing activities
Proceeds from issuance of Acquisition Corp			514
Reportable Legal Entities | WMG Acquisition Corp. | 4.125% Senior Secured Notes
Cash flows from financing activities
Repayment of Senior Secured Notes			(40)
Reportable Legal Entities | WMG Acquisition Corp. | 4.875% Senior Secured Notes
Cash flows from financing activities
Repayment of Senior Secured Notes			(30)
Reportable Legal Entities | WMG Acquisition Corp. | 5.625% Senior Secured Notes
Cash flows from financing activities
Repayment of Senior Secured Notes			(247)
Reportable Legal Entities | WMG Acquisition Corp. | 5.50% Senior Notes
Cash flows from financing activities
Proceeds from issuance of Acquisition Corp				325
Reportable Legal Entities | WMG Acquisition Corp. | 6.75% Senior Notes
Cash flows from financing activities
Repayment of and redemption deposit for Acquisition Corp. Senior Notes				(635)
Reportable Legal Entities | WMG Acquisition Corp. Consolidated
Cash flows from operating activities
Net income	14	321	167	325
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			203	205
Unrealized gains on remeasurement of foreign denominated loans			(6)	(6)
Deferred income taxes			25	105
Loss on extinguishment of debt	4	7	7	31
Net gain on divestitures and investments			(27)	(385)
Non-cash interest expense			5	5
Equity-based compensation expense			28	52
Changes in operating assets and liabilities:
Accounts receivable, net			(50)	(43)
Inventories			12	(1)
Royalty advances			(107)
Accounts payable and accrued liabilities			(94)	(84)
Royalty payables			117	113
Accrued interest			(13)	(22)
Deferred revenue			(17)	0
Other balance sheet changes			(1)	(30)
Net cash provided by operating activities			249	265
Cash flows from investing activities
Acquisition of music publishing rights, net			(24)	(11)
Capital expenditures			(82)	(40)
Investments and acquisitions of businesses, net			(234)	(14)
Proceeds from the sale of investments				516
Net cash (used in) provided by investing activities			(340)	451
Cash flows from financing activities
Call premiums paid on and redemption deposit for early redemption of debt			(5)	(23)
Deferred financing costs paid			(7)	(12)
Distribution to noncontrolling interest holder			(3)	(3)
Dividends paid			(63)	(425)
Net cash provided by (used in) financing activities			119	(453)
Proceeds from supplement of Acquisition Corp. Senior Term Loan Facility				320
Effect of exchange rate changes on cash and equivalents			(1)	(5)
Net increase in cash and equivalents			27	258
Cash and equivalents at beginning of period			514	647
Cash and equivalents at end of period	541	905	541	905
Reportable Legal Entities | WMG Acquisition Corp. Consolidated | 3.625% Senior Secured Notes due 2026
Cash flows from financing activities
Proceeds from issuance of Acquisition Corp			514
Reportable Legal Entities | WMG Acquisition Corp. Consolidated | 4.125% Senior Secured Notes
Cash flows from financing activities
Repayment of Senior Secured Notes			(40)
Reportable Legal Entities | WMG Acquisition Corp. Consolidated | 4.875% Senior Secured Notes
Cash flows from financing activities
Repayment of Senior Secured Notes			(30)
Reportable Legal Entities | WMG Acquisition Corp. Consolidated | 5.625% Senior Secured Notes
Cash flows from financing activities
Repayment of Senior Secured Notes			(247)
Reportable Legal Entities | WMG Acquisition Corp. Consolidated | 5.50% Senior Notes
Cash flows from financing activities
Proceeds from issuance of Acquisition Corp				325
Reportable Legal Entities | WMG Acquisition Corp. Consolidated | 6.75% Senior Notes
Cash flows from financing activities
Repayment of and redemption deposit for Acquisition Corp. Senior Notes				(635)
Reportable Legal Entities | WMG Holdings Corp.
Cash flows from operating activities
Net income	13	320	166	321
Adjustments to reconcile net income to net cash provided by operating activities:
Equity gains, including distributions			(166)	(321)
Eliminations
Cash flows from operating activities
Net income	(26)	(640)	(332)	(642)
Adjustments to reconcile net income to net cash provided by operating activities:
Equity gains, including distributions			332	642
Eliminations | WMG Acquisition Corp.
Cash flows from operating activities
Net income	$ (127)	$ (8)	(427)	(143)
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized gains on remeasurement of foreign denominated loans			0
Equity gains, including distributions			546	294
Changes in operating assets and liabilities:
Accounts payable and accrued liabilities			(119)	(151)
Cash flows from investing activities
Advances from issuer			8	108
Net cash (used in) provided by investing activities			8	108
Cash flows from financing activities
Change in due to (from) issuer			(8)	(108)
Net cash provided by (used in) financing activities			$ (8)	$ (108)