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BRBR (Details) - USD ($) shares in Millions, $ in Millions			12 Months Ended
	Nov. 25, 2022	Aug. 11, 2022	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Mar. 10, 2022
Schedule of Equity Method Investments [Line Items]
Gain on investment in BellRing			$ 0.0	$ (5.1)	$ (437.1)
Post | BellRing
Schedule of Equity Method Investments [Line Items]
Noncontrolling Interest, Common Stock, Amount					4.6	19.4
Noncontrolling Interest, Ownership Percentage by Parent						14.20%
Noncontrolling Interest, Common Stock, Transfer	4.6	14.8

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