Retirement Benefits and Postemployment Benefits (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	May 31, 2020	May 26, 2019	May 27, 2018
Defined Benefit Plan, Information About Plan Assets
Accumulated benefit obligation	$ 7,285.2	$ 6,436.9
Rate to which the cost trend rate is assumed to decline (ultimate rate)	4.50%	4.50%
Year that Rate Reaches Ultimate Trend Rate	2029	2029
Defined Contribution Plan Disclosure [Line Items]
Net assets of money purchase plan		$ 22.3
Recognized expense	$ 90.1	$ 52.7	$ 49.2
Under Age 65 [Member]
Defined Benefit Plan, Information About Plan Assets
Health care cost trend rate for next year	6.20%	6.40%
Over Age 65 [Member]
Defined Benefit Plan, Information About Plan Assets
Health care cost trend rate for next year	6.50%	6.70%
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 32.9	$ 30.4
Defined Benefit Plan, Information About Plan Assets
Projected benefit obligation at end of year	7,640.2	6,750.7	6,416.0
Plan assets at fair value	2,569.9	14.4
Projected benefit obligation	$ 3,512.9	589.7
Defined Benefit Pension Plans [Member] | United States Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	17.00%
Defined Benefit Pension Plans [Member] | International Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	11.00%
Defined Benefit Pension Plans [Member] | Private Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	9.00%
Defined Benefit Pension Plans [Member] | Fixed income [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	50.00%
Defined Benefit Pension Plans [Member] | Real asset investments [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	13.00%
Defined Benefit Pension Plans [Member] | United States [Member]
Defined Benefit Plan, Information About Plan Assets
Retirement Plan Provision Termination Period	5 years
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0.1	0.1
Defined Benefit Plan, Information About Plan Assets
Accumulated benefit obligation	479.4	498.4
Projected benefit obligation at end of year	773.7	824.1	871.8
Plan assets at fair value	248.0	233.7
Postemployment Benefit Plans [Member]
Defined Benefit Plan, Information About Plan Assets
Accumulated benefit obligation	150.3	128.0
Projected benefit obligation at end of year	$ 150.3	$ 128.0	$ 126.7
Postemployment Benefit Plans [Member] | United States Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	18.00%
Postemployment Benefit Plans [Member] | International Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	10.00%
Postemployment Benefit Plans [Member] | Private Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	4.00%
Postemployment Benefit Plans [Member] | Fixed income [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	65.00%
Postemployment Benefit Plans [Member] | Real asset investments [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	3.00%
General Mills Savings Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Net assets of money purchase plan	$ 20.6
ESOP number of allocated shares	4.6	5.1
Common stock held by ESOP and company stock fund	$ 464.8	$ 410.1