Business Segment and Geographic Information (Schedule of operating segment results) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Feb. 28, 2021	Feb. 23, 2020	Feb. 28, 2021	Feb. 23, 2020
Segment Reporting Information [Line Items]
Net sales	$ 4,520.0	$ 4,180.3	$ 13,603.4	$ 12,603.6
Operating profit	826.6	650.8	2,596.9	2,124.4
Restructuring, impairment, and other exit costs	11.0	5.8	11.9	12.9
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	4,520.0	4,180.3	13,603.4	12,603.6
Operating profit	813.1	748.3	2,707.1	2,412.2
Unallocated Corporate Items [Member]
Segment Reporting Information [Line Items]
Operating profit	(24.5)	91.7	98.3	274.9
North America Retail [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	2,726.8	2,501.9	8,355.3	7,554.1
Operating profit	605.7	532.0	2,002.8	1,734.4
U.S. Meals & Baking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	1,165.8	1,010.6	3,629.0	3,005.5
U.S. Cereal [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	614.1	563.9	1,862.3	1,725.6
U.S. Snacks [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	476.1	491.0	1,479.4	1,513.0
Canada [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	245.3	217.3	702.5	652.7
U.S. Yogurt & Other [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	225.5	219.1	682.1	657.3
Europe & Australia [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	484.2	421.9	1,442.6	1,308.9
Operating profit	29.4	22.1	118.3	81.1
Pet [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	436.3	383.5	1,288.0	1,140.0
Operating profit	102.3	94.0	311.9	255.7
Asia & Latin America [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	455.6	408.2	1,268.3	1,177.3
Operating profit	12.0	8.1	62.5	42.6
Convenience Stores & Foodservice [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	417.1	464.8	1,249.2	1,423.3
Operating profit	$ 63.7	$ 92.1	$ 211.6	$ 298.4

The net result for the period of deducting operating expenses from operating revenues.

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