Document and Entity Information - shares	6 Months Ended
	Mar. 31, 2019	May 07, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	wmg
Entity Registrant Name	Warner Music Group Corp.
Entity Central Index Key	0001319161
Current Fiscal Year End Date	--09-30
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		1,060