Guarantor and Non-Guarantor Subsidiaries Financial Information - Consolidating Statement of Cash Flows Unaudited (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Net income	$ 67	$ (1)	$ 153	$ 4
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			137	134
Unrealized (gains) losses and remeasurement of foreign denominated loans			(24)	11
Deferred income taxes			27	38
Loss on extinguishment of debt		23	3	24
Net gain on divestitures and investments			(32)	(7)
Non-cash interest expense			3	3
Equity-based compensation expense			14	27
Changes in operating assets and liabilities:
Accounts receivable			(90)	(15)
Inventories			13	1
Royalty advances			(61)	(12)
Accounts payable and accrued liabilities			(100)	(100)
Royalty payables			46	68
Accrued interest			1	(14)
Deferred revenue			(19)	(16)
Other balance sheet changes			28	(10)
Net cash provided by operating activities			99	136
Cash flows from investing activities
Acquisition of music publishing rights, net			(16)	(5)
Capital expenditures			(59)	(29)
Investments and acquisitions of businesses, net			(218)	(6)
Proceeds from the sale of investments				12
Net cash used in investing activities			(293)	(28)
Cash flows from financing activities
Call premiums paid on and redemption deposit for early redemption of debt			(2)	(23)
Deferred financing costs paid			(4)	(9)
Distribution to noncontrolling interest holder			(2)	(2)
Dividends paid			(31)	(125)
Net cash provided by (used in) financing activities			151	(149)
Proceeds from supplement of Acquisition Corp. Senior Term Loan Facility				320
Effect of exchange rate changes on cash and equivalents			(1)	6
Net decrease in cash and equivalents			(44)	(35)
Cash and equivalents at beginning of period			514	647
Cash and equivalents at end of period	470	612	470	612
3.625% Senior Secured Notes due 2026
Cash flows from financing activities
Proceeds from issuance of Acquisition Corp			287
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			(27)
5.50% Senior Notes
Cash flows from financing activities
Proceeds from issuance of Acquisition Corp				325
6.75% Senior Notes
Cash flows from financing activities
Repayment of and redemption deposit for Acquisition Corp. Senior Notes				(635)
Reportable Legal Entities | Guarantor Subsidiaries
Cash flows from operating activities
Net income	73	40	201	74
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			68	67
Unrealized (gains) losses and remeasurement of foreign denominated loans			(5)	3
Net gain on divestitures and investments			(30)	(7)
Equity-based compensation expense			14	27
Equity gains, including distributions			(143)	(76)
Changes in operating assets and liabilities:
Accounts receivable			(16)	(16)
Inventories			4	(1)
Royalty advances			(37)	(20)
Accounts payable and accrued liabilities			218	101
Royalty payables			(93)	48
Deferred revenue			(44)	9
Other balance sheet changes			41	43
Net cash provided by operating activities			178	252
Cash flows from investing activities
Acquisition of music publishing rights, net			(11)	(4)
Capital expenditures			(50)	(23)
Investments and acquisitions of businesses, net			(26)	(6)
Proceeds from the sale of investments				12
Net cash used in investing activities			(87)	(21)
Cash flows from financing activities
Distribution to noncontrolling interest holder			(1)
Dividends paid			(31)	(98)
Change in due to (from) issuer			24	(151)
Net cash provided by (used in) financing activities			(8)	(249)
Net decrease in cash and equivalents			83	(18)
Cash and equivalents at beginning of period			169	347
Cash and equivalents at end of period	252	329	252	329
Reportable Legal Entities | Non-Guarantor Subsidiaries
Cash flows from operating activities
Net income	15	23	99	64
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			69	67
Unrealized (gains) losses and remeasurement of foreign denominated loans				(9)
Deferred income taxes			27	38
Net gain on divestitures and investments			(2)
Changes in operating assets and liabilities:
Accounts receivable			(74)	1
Inventories			9	2
Royalty advances			(24)	8
Accounts payable and accrued liabilities			(172)	(104)
Royalty payables			133	20
Deferred revenue			25	(25)
Other balance sheet changes			(17)	(49)
Net cash provided by operating activities			73	13
Cash flows from investing activities
Acquisition of music publishing rights, net			(5)	(1)
Capital expenditures			(9)	(6)
Investments and acquisitions of businesses, net			(192)
Net cash used in investing activities			(206)	(7)
Cash flows from financing activities
Distribution to noncontrolling interest holder			(1)	(2)
Dividends paid				(27)
Net cash provided by (used in) financing activities			(1)	(29)
Effect of exchange rate changes on cash and equivalents			(1)	6
Net decrease in cash and equivalents			(135)	(17)
Cash and equivalents at beginning of period			345	300
Cash and equivalents at end of period	210	283	210	283
Reportable Legal Entities | Warner Music Group Corp.
Cash flows from operating activities
Net income	67	(3)	153	1
Adjustments to reconcile net income to net cash provided by operating activities:
Equity gains, including distributions			(153)	(1)
Reportable Legal Entities | WMG Acquisition Corp.
Cash flows from operating activities
Net income	67	(3)	153	1
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized (gains) losses and remeasurement of foreign denominated loans			(20)	17
Loss on extinguishment of debt		23	3	24
Non-cash interest expense			3	3
Equity gains, including distributions			(302)	(156)
Changes in operating assets and liabilities:
Royalty payables			6
Accrued interest			1	(14)
Other balance sheet changes			4	(4)
Net cash provided by operating activities			(152)	(129)
Cash flows from investing activities
Advances from issuer			(24)	151
Net cash used in investing activities			(24)	151
Cash flows from financing activities
Call premiums paid on and redemption deposit for early redemption of debt			(2)	(23)
Deferred financing costs paid			(4)	(9)
Net cash provided by (used in) financing activities			184	(22)
Proceeds from supplement of Acquisition Corp. Senior Term Loan Facility				320
Net decrease in cash and equivalents			8
Cash and equivalents at end of period	8		8
Reportable Legal Entities | WMG Acquisition Corp. | 3.625% Senior Secured Notes due 2026
Cash flows from financing activities
Proceeds from issuance of Acquisition Corp			287
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			(27)
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	67	(1)	153	4
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			137	134
Unrealized (gains) losses and remeasurement of foreign denominated loans			(24)	11
Deferred income taxes			27	38
Loss on extinguishment of debt		23	3	24
Net gain on divestitures and investments			(32)	(7)
Non-cash interest expense			3	3
Equity-based compensation expense			14	27
Changes in operating assets and liabilities:
Accounts receivable			(90)	(15)
Inventories			13	1
Royalty advances			(61)	(12)
Accounts payable and accrued liabilities			(100)	(100)
Royalty payables			46	68
Accrued interest			1	(14)
Deferred revenue			(19)	(16)
Other balance sheet changes			28	(10)
Net cash provided by operating activities			99	136
Cash flows from investing activities
Acquisition of music publishing rights, net			(16)	(5)
Capital expenditures			(59)	(29)
Investments and acquisitions of businesses, net			(218)	(6)
Proceeds from the sale of investments				12
Net cash used in investing activities			(293)	(28)
Cash flows from financing activities
Call premiums paid on and redemption deposit for early redemption of debt			(2)	(23)
Deferred financing costs paid			(4)	(9)
Distribution to noncontrolling interest holder			(2)	(2)
Dividends paid			(31)	(125)
Net cash provided by (used in) financing activities			151	(149)
Proceeds from supplement of Acquisition Corp. Senior Term Loan Facility				320
Effect of exchange rate changes on cash and equivalents			(1)	6
Net decrease in cash and equivalents			(44)	(35)
Cash and equivalents at beginning of period			514	647
Cash and equivalents at end of period	470	612	470	612
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			287
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			(27)
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	67	(3)	153	1
Adjustments to reconcile net income to net cash provided by operating activities:
Equity gains, including distributions			(153)	(1)
Eliminations
Cash flows from operating activities
Net income	(134)	6	(306)	(2)
Adjustments to reconcile net income to net cash provided by operating activities:
Equity gains, including distributions			306	2
Eliminations | WMG Acquisition Corp.
Cash flows from operating activities
Net income	$ (88)	$ (61)	(300)	(135)
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized (gains) losses and remeasurement of foreign denominated loans			1
Equity gains, including distributions			445	232
Changes in operating assets and liabilities:
Accounts payable and accrued liabilities			(146)	(97)
Cash flows from investing activities
Advances from issuer			24	(151)
Net cash used in investing activities			24	(151)
Cash flows from financing activities
Change in due to (from) issuer			(24)	151
Net cash provided by (used in) financing activities			$ (24)	$ 151