Acquisition and Divestitures (Acquisition Pro forma Information) (Details) - Business Acquisition, Blue Buffalo [Member] - USD ($) $ in Millions	12 Months Ended
May 27, 2018	May 28, 2017
Business Acquisition, Pro Forma Information [Abstract]
Net sales (pro forma)	$ 17,057.4	$ 16,772.9
Net earnings attributable to General Mills (pro forma)	$ 2,252.4	$ 1,540.2

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

Name:	us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration