Earnings per Share (Schedule of earnings per share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
		Aug. 26, 2018	Aug. 27, 2017
Earnings Per Share [Abstract]
Net earnings attributable to General Mills		$ 392.3	$ 404.7
Average number of common shares - basic EPS		598.0	576.5
Earnings Per Share, Basic and Diluted [Abstract]
Average number of common shares - diluted EPS		603.3	586.9
Earnings per share - basic		$ 0.66	$ 0.7
Earnings per share - diluted		$ 0.65	$ 0.69
Other Disclosures [Abstract]
Anti-dilutive stock options, restricted stock units and performance share units		14.3	5.4
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Incremental share effect	[1]	3.6	8.3
Restricted Stock, Restricted Stock Units, and Other [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Incremental share effect	[1]	1.7	2.1

[1] Incremental shares from stock options, restricted stock units, and performance share units are computed by the treasury stock method.