Comprehensive Income (Loss) - Additional Information (Detail) $ in Millions	3 Months Ended
Dec. 31, 2017 USD ($)
Equity [Abstract]
Changes in accumulated other comprehensive loss, net of related taxes	$ 7

Changes in accumulated other comprehensive income loss net of related tax.

No definition available.

Name:	wmg_ChangesInAccumulatedOtherComprehensiveIncomeLossNetOfRelatedTax
Namespace Prefix:	wmg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration