Stockholders' Equity (Schedule of total comprehensive income (loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2021	Feb. 23, 2020	Feb. 28, 2021	Feb. 23, 2020
Other Comprehensive Income (Loss), Net of Tax:
Net earnings attributable to General Mills	$ 595.7	$ 454.1	$ 1,923.0	$ 1,555.5
Net earnings attributable to redeemable and noncontrolling interests	8.1	9.8	23.1	28.3
Foreign currency translation	12.5	(22.0)	102.4	(28.5)
Other fair value changes:
Hedge derivatives	0.1	(6.4)	(10.1)	(15.4)
Reclassification to earnings:
Hedge derivatives	5.4	4.0	4.7	3.6
Amortization of losses and prior service costs	19.8	19.6	59.1	58.8
Other comprehensive income (loss), net of tax	37.8	(4.8)	156.1	18.5
Total comprehensive income (loss) attributable to General Mills	620.6	459.4	1,994.7	1,596.4
General Mills [Member]
Other comprehensive income (loss):
Foreign currency translation	(7.8)	(11.7)	(41.4)	(7.3)
Other fair value changes:
Hedge derivatives	2.5	(7.7)	(11.1)	(16.9)
Reclassification to earnings:
Hedge derivatives	6.8	4.7	6.7	4.5
Amortization of losses and prior service costs	25.6	25.4	76.7	76.4
Other comprehensive income (loss):	27.1	10.7	30.9	56.7
Other comprehensive income (loss):
Foreign currency translation	6.7	0.0	58.3	0.0
Other fair value changes:
Hedge derivatives	(1.5)	1.1	2.0	2.7
Reclassification to earnings:
Hedge derivatives	(1.6)	(0.7)	(1.9)	(0.9)
Amortization of losses and prior service costs (b)	(5.8)	(5.8)	(17.6)	(17.6)
Other comprehensive income (loss), tax	(2.2)	(5.4)	40.8	(15.8)
Other Comprehensive Income (Loss), Net of Tax:
Net earnings attributable to General Mills	595.7	454.1	1,923.0	1,555.5
Foreign currency translation	(1.1)	(11.7)	16.9	(7.3)
Other fair value changes:
Hedge derivatives	1.0	(6.6)	(9.1)	(14.2)
Reclassification to earnings:
Hedge derivatives	5.2	4.0	4.8	3.6
Amortization of losses and prior service costs	19.8	19.6	59.1	58.8
Other comprehensive income (loss), net of tax	24.9	5.3	71.7	40.9
Total comprehensive income (loss) attributable to General Mills	620.6	459.4	1,994.7	1,596.4
Noncontrolling Interests [Member]
Other Comprehensive Income (Loss), Net of Tax:
Net earnings attributable to redeemable and noncontrolling interests	1.1	3.2	3.9	11.7
Foreign currency translation	2.6	(4.7)	27.9	(9.5)
Other fair value changes:
Hedge derivatives	0.0	0.0	0.0	0.0
Reclassification to earnings:
Hedge derivatives	0.0	0.0	0.0	0.0
Amortization of losses and prior service costs	0.0	0.0	0.0	0.0
Other comprehensive income (loss), net of tax	2.6	(4.7)	27.9	(9.5)
Total comprehensive income (loss) attributable to noncontrolling interests	3.7	(1.5)	31.8	2.2
Redeemable Interests [Member]
Other Comprehensive Income (Loss), Net of Tax:
Net earnings attributable to redeemable and noncontrolling interests	7.0	6.6	19.2	16.6
Foreign currency translation	11.0	(5.6)	57.6	(11.7)
Other fair value changes:
Hedge derivatives	(0.9)	0.2	(1.0)	(1.2)
Reclassification to earnings:
Hedge derivatives	0.2	0.0	(0.1)	0.0
Amortization of losses and prior service costs	0.0	0.0	0.0	0.0
Other comprehensive income (loss), net of tax	10.3	(5.4)	56.5	(12.9)
Total comprehensive income (loss) attributable to redeemable interests	$ 17.3	$ 1.2	$ 75.7	$ 3.7