Stock Plans (Schedule of compensation expense related to stock-based payments) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Feb. 28, 2021	Feb. 23, 2020	Feb. 28, 2021	Feb. 23, 2020
Stock Plans [Abstract]
Compensation expense related to stock-based payments	$ 20.8	$ 18.2	$ 69.5	$ 66.0

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees, including any applicable restructuring items and non-cash items.

No definition available.

Name:	gis_AllocatedShareBasedCompensationExpenseIncludingRestructuringAndNoncashItems
Namespace Prefix:	gis_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration