Risk Management Activities (Schedule of unallocated corporate items) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 27, 2016	Nov. 29, 2015	Nov. 27, 2016	Nov. 29, 2015
Commodity Price Risk [Abstract]
Net gain (loss) on mark-to-market valuation of certain commodity positions	$ 3.0	$ (31.7)	$ (15.9)	$ (54.0)
Net loss on commodity positions reclassified from unallocated corporate items to segment operating profit	14.4	35.2	23.7	62.1
Net mark-to-market revaluation of certain grain inventories	11.7	4.2	4.7	2.3
Net mark-to-market valuation of certain commodity positions recognized in unallocated corporate items	$ 29.1	$ 7.7	$ 12.5	$ 10.4