Derivative Financial Instruments - Narrative (Details) - USD ($) shares in Millions, $ in Millions				12 Months Ended
		Nov. 15, 2023	Apr. 28, 2023	Apr. 30, 2025		Apr. 30, 2024		Apr. 30, 2023	Apr. 30, 2020
Derivative Financial Instruments (Textual) [Abstract]
Collateral received						$ 1.9
Collateral pledged				$ 37.5
Cumulative net mark-to-market valuation of certain derivative positions recognized in unallocated derivative gains (losses)				80.8		22.6
Settlement of interest rate contracts				0.0		42.5		$ 0.0
Interest expense – net				(388.7)		(264.3)		(152.0)
Other income (expense) – net	[1]			(14.4)		(25.6)		(14.7)
Loss (Gain) on Reverse Tresaury Lock				4.5
Other debt gains (charges) – net	[2]			$ 30.2	[1]	(19.5)	[1]	$ 0.0
Post Holdings Inc. | Pet Food Brands
Derivative Financial Instruments (Textual) [Abstract]
Proceeds from Divestiture of Business, Equity		5.4	5.4
Proceeds from investment in equity securities		$ 466.3
Commodity contracts
Derivative Financial Instruments (Textual) [Abstract]
Derivative instrument maturity				1 year
Foreign currency exchange contracts
Derivative Financial Instruments (Textual) [Abstract]
Derivative instrument maturity				1 year
Forward Contracts | Post Holdings Inc. | Pet Food Brands
Derivative Financial Instruments (Textual) [Abstract]
Gain (loss) on derivative - net				$ 5.4
Interest rate contract
Derivative Financial Instruments (Textual) [Abstract]
Settlement of interest rate contracts						42.5
Deferred pre-tax net gain (loss) included in accumulated other comprehensive loss									$ (239.8)
Deferred Gain (Loss) on Cash Flow Hedges Included in Accumulated Other Comprehensive Income or Loss				(117.4)		(187.1)
Tax impact related to deferred losses and gains on cash flow hedges included in accumulated other comprehensive loss				27.3		$ 44.0
Effective portion of the hedge loss reclassified to interest expense over the next twelve months				$ (12.5)

[1] Includes special project costs related to certain divestiture, acquisition, integration, and restructuring activities. For more information, see Note 4: Special Project Costs and Note 8: Debt and Financing Arrangements.

[2] Includes special project costs related to certain divestiture, acquisition, integration, and restructuring activities. For more information, see Note 4: Special Project Costs, Note 5: Reportable Segments, and Note 8: Debt and Financing Arrangements.