Business Segment and Geographic Information (Schedule of net sales by class of similar products) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2021	Feb. 23, 2020	Feb. 28, 2021	Feb. 23, 2020
Product Information [Line Items]
Net sales	$ 4,520.0	$ 4,180.3	$ 13,603.4	$ 12,603.6
Snacks [Member]
Product Information [Line Items]
Net sales	871.9	840.4	2,608.6	2,547.7
Convenient meals [Member]
Product Information [Line Items]
Net sales	785.0	706.0	2,334.8	1,961.2
Cereal [Member]
Product Information [Line Items]
Net sales	715.4	674.5	2,168.7	2,048.1
Yogurt [Member]
Product Information [Line Items]
Net sales	505.3	499.8	1,513.5	1,510.1
Dough [Member]
Product Information [Line Items]
Net sales	498.0	440.6	1,456.8	1,309.6
Baking mixes and ingredients [Member]
Product Information [Line Items]
Net sales	416.8	394.6	1,293.6	1,211.6
Pet [Member]
Product Information [Line Items]
Net sales	436.3	383.5	1,288.0	1,140.0
Super-premium ice cream [Member]
Product Information [Line Items]
Net sales	164.0	131.5	596.4	551.3
Other [Member]
Product Information [Line Items]
Net sales	$ 127.3	$ 109.4	$ 343.0	$ 324.0