Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Numerator
Net income attributable to Warner Music Group Corp.	$ 365	$ 435	$ 430
Denominator
Dilutive effect of potentially issuable shares (in shares)	397,000	0	0
Class A
Numerator
Net income attributable to Warner Music Group Corp.	$ 105	$ 122	$ 119
Less: Net income attributable to participating securities	(4)	(6)	(6)
Net income attributable to common stockholders	$ 101	$ 116	$ 113
Denominator
Weighted average shares outstanding, basic (in shares)	145,128,000	140,882,000	138,070,000
Weighted average shares outstanding, diluted (in shares)	145,128,000	140,882,000	138,070,000
Basic EPS (in dollars per share)	$ 0.69	$ 0.83	$ 0.82
Diluted EPS (in dollars per share)	$ 0.69	$ 0.83	$ 0.82
Class B
Numerator
Net income attributable to Warner Music Group Corp.	$ 260	$ 313	$ 311
Less: Net income attributable to participating securities	0	0	0
Net income attributable to common stockholders	$ 260	$ 313	$ 311
Denominator
Weighted average shares outstanding, basic (in shares)	375,380,000	376,641,000	377,650,000
Weighted average shares outstanding, diluted (in shares)	375,380,000	376,641,000	377,650,000
Basic EPS (in dollars per share)	$ 0.69	$ 0.83	$ 0.82
Diluted EPS (in dollars per share)	$ 0.69	$ 0.83	$ 0.82