Financial Instruments, Risk Management Activities, and Fair Values (Schedule of unallocated corporate items) (Details) - USD ($) $ in Millions	12 Months Ended
	May 29, 2016	May 31, 2015	May 25, 2014
Commodity Price Risk [Abstract]
Net gain (loss) on mark-to-market valuation of commodity positions	$ (69.1)	$ (163.7)	$ (4.9)
Net loss (gain) on commodity positions reclassified from unallocated corporate items to segment operating profit	127.9	84.4	51.2
Net mark-to-market revaluation of certain grain inventories	4.0	(10.4)	2.2
Net mark-to-market valuation of certain commodity positions recognized in unallocated corporate items	$ 62.8	$ (89.7)	$ 48.5