Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Class of Stock [Line Items]
Total share repurchase cost	$ 9.4	$ 41.2
BellRing Common Stock | Common Stock
Class of Stock [Line Items]
Shares repurchased	0.2	1.8
Average price per share	$ 44.27	$ 23.33
Total share repurchase cost	$ 9.4	$ 41.2