Supplemental Information (Schedule of certain Consolidated Balance Sheet accounts) (Details) - USD ($) $ in Millions	May 31, 2020	May 26, 2019	May 27, 2018	May 28, 2017
Receivables [Abstract]
Customers	$ 1,648.3	$ 1,708.5
Less allowance for doubtful accounts	(33.2)	(28.8)
Total	1,615.1	1,679.7
Inventories [Abstract]
Finished goods	1,142.6	1,245.9
Raw materials and packaging	392.2	434.9
Grain	93.6	92.0
Excess of FIFO over LIFO cost	(202.1)	(213.5)
Total	1,426.3	1,559.3
LIFO Inventory Amount	892.6	974.8
Prepaid Expenses and Other Current Assets [Abstract]
Prepaid expenses	194.5	189.0
Other receivables	85.2	250.2
Derivative receivables, primarily commodity-related	70.6	42.2
Grain contracts	5.0	6.7
Miscellaneous	46.8	9.4
Total	402.1	497.5
Land, Buildings and Equipment [Abstract]
Equipment	6,428.0	6,548.3
Buildings	2,412.6	2,477.2
Capitalized software	668.5	631.6
Construction in progress	373.5	343.8
Land	66.1	73.6
Total land, buildings, and equipment	9,954.8	10,080.5
Less accumulated depreciation	(6,374.2)	(6,293.3)
Total	3,580.6	3,787.2
Other Assets [Abstract]
Investments in and advances to joint ventures	566.7	452.9
Operating Lease Right Of Use Asset	$ 365.2	$ 0.0
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets	us-gaap:OtherAssets
Pension assets	$ 21.2	$ 323.5
Life insurance	19.5	22.7
Miscellaneous	113.2	175.8
Total	1,085.8	974.9
Other Current Liabilities [Abstract]
Accrued trade and consumer promotions	550.4	484.4
Accrued payroll	430.4	345.5
Operating Lease Liability Current	$ 102.0	$ 0.0
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Total	Total
Accrued interest, including interest rate swaps	$ 92.8	$ 92.6
Accrued taxes	80.3	37.5
Derivative payable	39.2	13.2
Dividends payable	20.7	19.2
Restructuring and other exit costs reserve	17.8	36.5	$ 66.8	$ 85.0
Grains contracts	1.2	2.3
Miscellaneous	298.5	336.6
Total	1,633.3	1,367.8
Other Noncurrent Liabilities [Abstract]
Accrued compensation and benefits, including obligations for underfunded other postretirement benefit and postemployment benefit plans	958.7	1,153.3
Operating Lease Liability Noncurrent	$ 277.0	$ 0.0
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilities	us-gaap:OtherLiabilities
Accrued taxes	$ 238.6	$ 227.1
Miscellaneous	70.7	68.5
Total	1,545.0	1,448.9
Buildings [Member]
Land, Buildings and Equipment [Abstract]
Capital leased assets	0.3	0.3
Equipment [Member]
Land, Buildings and Equipment [Abstract]
Capital leased assets	$ 5.8	$ 5.7