Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Mar. 10, 2022
Income Tax Disclosure
Effective income tax rate	20.30%	7.10%	8.40%
Undistributed earnings of foreign subsidiaries	$ 1.7	$ 1.0
Income (loss) from continuing operations before income taxes, foreign	$ 1.1	$ (1.9)	$ (0.8)
BellRing Common Stock | Old BellRing Stockholders
Income Tax Disclosure
BellRing Common Stock Ownership Percentage		28.80%	28.80%	28.50%