Retirement Benefits and Postemployment Benefits (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	May 28, 2017		May 29, 2016	May 31, 2015
Defined Benefit Plan, Information About Plan Assets
Accumulated benefit obligation	$ 6,104.5		$ 5,950.7
Increase (decrease) in service and interest cost for current period resulting from change in estimate methodology	$ (68.0)
Expected rate of return on plan assets	8.25%
Defined Contribution Plan Disclosure [Line Items]
Net assets of money purchase plan	$ 23.0		21.0
Recognized expense	$ 54.1		$ 61.2	$ 44.0
General Mills Savings Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
ESOP number of allocated shares	6.3		6.9
Common stock held by ESOP and company stock fund	$ 598.7		$ 711.5
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 25.4		$ 23.7
Defined Benefit Plan, Information About Plan Assets
Expected rate of return on plan assets	8.17%	[1]	8.53%	8.53%
Defined Benefit Pension Plans [Member] | United States Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	20.00%
Defined Benefit Pension Plans [Member] | International Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	15.00%
Defined Benefit Pension Plans [Member] | Private Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	10.00%
Defined Benefit Pension Plans [Member] | Fixed income [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	40.00%
Defined Benefit Pension Plans [Member] | Real assets [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	15.00%
U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0.0		$ 0.0	$ 0.0
Defined Benefit Plan, Information About Plan Assets
Retirement Plan Provision Termination Period	5 years
Decline in projected benefit obligation as of fiscal year end	$ 130.9
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 20.1		$ 24.1
Defined Benefit Plan, Information About Plan Assets
Expected rate of return on plan assets	7.85%	[1]	8.14%	8.13%
Other Postretirement Benefit Plans [Member] | United States Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	30.00%
Other Postretirement Benefit Plans [Member] | International Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	15.00%
Other Postretirement Benefit Plans [Member] | Private Equities [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	10.00%
Other Postretirement Benefit Plans [Member] | Fixed income [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	40.00%
Other Postretirement Benefit Plans [Member] | Real assets [Member]
Defined Benefit Plan, Information About Plan Assets
Target Allocation, Percentage of Assets Equity Securities	5.00%
United States Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 20.0		$ 24.1
Postemployment Benefit Plans [Member]
Defined Benefit Plan, Information About Plan Assets
Expected rate of return on plan assets	0.00%	[1]	0.00%	0.00%

[1] (a) Beginning in fiscal 2017, we adopted the full yield curve method.