Stockholders' Equity (Schedule of total comprehensive income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2020	Feb. 23, 2020	Nov. 24, 2019	Aug. 25, 2019	May 26, 2019	Feb. 24, 2019	Nov. 25, 2018	Aug. 26, 2018	May 31, 2020	May 26, 2019	May 27, 2018
Other comprehensive income (loss), net of tax:
Foreign currency translation									$ (169.1)	$ (82.8)	$ (37.0)
Net actuarial income (loss)									(224.6)	(253.4)	140.1
Other fair value changes:
Securities									0.0	0.0	1.2
Hedge derivatives									3.2	12.1	(50.8)
Reclassification to earnings:
Securities									0.0	(2.0)	(5.1)
Hedge derivatives									4.1	0.9	17.4
Amortization of losses and prior service costs									77.9	84.6	117.6
Other comprehensive income (loss), net of tax									(308.5)	(240.6)	183.4
Comprehensive Income:
Net earnings attributable to General Mills	$ 625.7	$ 454.1	$ 580.8	$ 520.6	$ 570.2	$ 446.8	$ 343.4	$ 392.3	2,181.2	1,752.7	2,131.0
Net earnings attributable to redeemable and noncontrolling interests									29.6	33.5	32.0
Total comprehensive income (loss) attributable to General Mills									1,892.2	1,556.3	2,275.9
General Mills [Member]
Other comprehensive income (loss), before tax:
Foreign currency translation									(149.1)	(38.3)	(76.9)
Net actuarial income (loss)									(290.2)	(325.6)	185.5
Other fair value chages:
Securities											1.8
Hedge derivaties									4.4	15.9	(64.7)
Reclassification to earnings:
Securities										(2.6)	(6.6)
Hedge derivatives									4.3	0.1	24.9
Amortization of losses and prior service costs									101.3	107.5	176.8
Other comprehensive income (loss), before tax									(329.3)	(243.0)	240.8
Other comprehensive income (loss), tax:
Foreign currency translation									0.0	0.0	0.0
Net actuarial income (loss)									65.6	72.2	(45.4)
Other fair value changes:
Securities											(0.6)
Hedge derivatives									(1.2)	(3.7)	14.2
Reclassification to earnings:
Securities										0.6	1.5
Hedge derivatives									(0.7)	0.4	(6.4)
Amortization of losses and prior service costs									(23.4)	(22.9)	(59.2)
Other comprehensive income (loss), tax									40.3	46.6	(95.9)
Other comprehensive income (loss), net of tax:
Foreign currency translation									(149.1)	(38.3)	(76.9)
Net actuarial income (loss)									(224.6)	(253.4)	140.1
Other fair value changes:
Securities											1.2
Hedge derivatives									3.2	12.2	(50.5)
Reclassification to earnings:
Securities										(2.0)	(5.1)
Hedge derivatives									3.6	0.5	18.5
Amortization of losses and prior service costs									77.9	84.6	117.6
Other comprehensive income (loss), net of tax									(289.0)	(196.4)	144.9
Comprehensive Income:
Net earnings attributable to General Mills									2,181.2	1,752.7	2,131.0
Total comprehensive income (loss) attributable to General Mills									1,892.2	1,556.3	2,275.9
Noncontrolling Interests [Member]
Other comprehensive income (loss), net of tax:
Foreign currency translation									(2.6)	(13.5)	13.5
Net actuarial income (loss)									0.0	0.0	0.0
Other fair value changes:
Securities											0.0
Hedge derivatives									0.0	0.0	0.0
Reclassification to earnings:
Securities										0.0	0.0
Hedge derivatives									0.0	0.0	0.0
Amortization of losses and prior service costs									0.0	0.0	0.0
Other comprehensive income (loss), net of tax									(2.6)	(13.5)	13.5
Comprehensive Income:
Net earnings attributable to redeemable and noncontrolling interests									12.9	13.9	13.4
Total comprehensive income (loss) attributable to noncontrolling interests									10.3	0.4	26.9
Redeemable Interest [Member]
Other comprehensive income (loss), net of tax:
Foreign currency translation									(17.4)	(31.0)	26.4
Net actuarial income (loss)									0.0	0.0	0.0
Other fair value changes:
Securities											0.0
Hedge derivatives									0.0	(0.1)	(0.3)
Reclassification to earnings:
Securities										0.0	0.0
Hedge derivatives									0.5	0.4	(1.1)
Amortization of losses and prior service costs									0.0	0.0	0.0
Other comprehensive income (loss), net of tax									(16.9)	(30.7)	25.0
Comprehensive Income:
Net earnings attributable to redeemable and noncontrolling interests									16.7	19.6	18.6
Total comprehensive income (loss) attributable to redeemable interests									$ (0.2)	$ (11.1)	$ 43.6