Accounting Policies - Narrative (Details) shares in Millions, $ in Millions			12 Months Ended
	Nov. 15, 2023 USD ($) shares	Apr. 28, 2023 USD ($) shares	Apr. 30, 2024 USD ($) Facility Contract	Apr. 30, 2023 USD ($)	Apr. 30, 2022 USD ($)	Apr. 30, 2021 USD ($)
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents			$ 62.0	$ 655.8	$ 169.9	$ 334.3
Advertising expense			182.5	160.3	176.5
Reserve for credit loss			8.7	2.3
Unrealized pre-tax gains included in accumulated other comprehensive income (loss) on available-for-sale securities			1.4	1.8
Accumulated other comprehensive income (loss)			$ (234.6)	(239.2)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for share-based payments			3 years
Compensation cost related to nonvested share-based awards not yet recognized			$ 41.5
Weighted-average period of recognition			2 years
Excess tax benefit from share-based compensation			$ 2.9	1.4	1.1
Accounting Policies (Additional Textual) [Abstract]
Charges for defined contribution plans			41.5	41.0	40.9
Property, Plant and Equipment [Line Items]
Operating Lease, Expense			121.7	113.3	111.0
Schedule of Investments [Line Items]
Investment in equity securities			0.0	487.8
Realized loss on investment in equity securities – net			$ (21.5)	0.0	0.0
Concentration Risk [Line Items]
Facilities covered by union contracts | Facility			11
Number of union contracts expiring in 2025 | Contract			6
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Accumulated other comprehensive income (loss)			$ (39.2)	(34.3)	(21.1)	$ (9.0)
Selling, Distribution And Administrative Expense
Condensed Financial Statements, Captions [Line Items]
Distribution costs			267.7	304.5	294.1
Research and development costs			$ 49.1	$ 47.3	$ 48.8
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for share-based payments			1 year
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for share-based payments			3 years
Machinery and equipment [Member] | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of assets			3 years
Machinery and equipment [Member] | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of assets			20 years
Capitalized software costs [Member] | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of assets			1 year
Capitalized software costs [Member] | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of assets			7 years
Buildings, fixtures, and improvements [Member] | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of assets			5 years
Buildings, fixtures, and improvements [Member] | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of assets			40 years
Post Holdings Inc.
Schedule of Investments [Line Items]
Investment in equity securities, current, ownership percentage				8.00%
Cumulative realized loss on investment in equity securities - net			$ 30.7
Realized loss on investment in equity securities – net			$ 26.9	$ 3.8
Post Holdings Inc. | Pet Food Brands
Schedule of Investments [Line Items]
Proceeds from Divestiture of Business, Equity | shares	5.4	5.4
Investment in equity securities	$ 460.9	$ 491.6		487.8
Mountain Country Foods [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of equity interest acquired			20.00%
Numi, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of equity interest acquired			42.00%
Unionized Employees [Member] | Number of Employees, Total [Member]
Concentration Risk [Line Items]
Percentage of concentration risk			27.00%
Unionized Employees Subject to Union Contracts Expiring within One Year | Number of Employees, Total [Member]
Concentration Risk [Line Items]
Percentage of concentration risk			10.00%
Cash Equivalents [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents			$ 0.0	614.0
Work In Process Inventory
Condensed Financial Statements, Captions [Line Items]
Work-in-process inventory			81.3	82.5
Other Noncurrent Assets
Condensed Financial Statements, Captions [Line Items]
Marketable securities and other investments			22.1	24.0
Accounts Payable [Member]
Condensed Financial Statements, Captions [Line Items]
Supplier Financing, Outstanding Payment Obligations			$ 384.9	$ 414.2