Note 1 - Summary of Significant Accounting Policies - Reclassification from Other Comprehensive Income (Loss) to Income (Details) - USD ($) $ in Millions	12 Months Ended
	May 29, 2022	May 30, 2021	May 31, 2020
Interest expense, net, cash flow hedges	$ (379.9)	$ (420.4)	$ (487.1)
Selling, general and administrative expenses	1,492.8	1,403.0	1,622.5
Equity method investment earnings	145.3	84.4	73.2
Total before tax	1,033.4	1,410.3	969.9
Income tax expense	290.5	193.8	201.3
Net of tax	888.2	1,298.8	840.1
Pension and postretirement non-service income	(67.3)	(54.5)	(9.9)
Total before tax	1,033.4	1,410.3	969.9
Income tax expense	290.5	193.8	201.3
Net income attributable to Conagra Brands, Inc.	888.2	1,298.8	840.1
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Interest expense, net, cash flow hedges	(3.1)	(3.2)	(3.3)
Selling, general and administrative expenses	0.0	(0.5)	0.0
Equity method investment earnings	1.8	2.1	0.0
Total before tax	(1.3)	(1.6)	(3.3)
Income tax expense	0.4	1.0	0.9
Net of tax	(0.9)	(0.6)	(2.4)
Total before tax	(1.3)	(1.6)	(3.3)
Income tax expense	0.4	1.0	0.9
Net income attributable to Conagra Brands, Inc.	(0.9)	(0.6)	(2.4)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Pension and postretirement non-service income	0.1	0.2	0.6
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Pension and postretirement non-service income	(3.6)	(3.5)	(4.6)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans, Adjustment Settlement, Attributable to Parent [Member] | Pension Plan [Member]
Pension and postretirement non-service income	0.0	0.0	(2.1)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans, Adjustment Settlement, Attributable to Parent [Member] | Postretirement Health Coverage [Member]
Pension and postretirement non-service income	0.0	(0.5)	(0.2)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans, Adjustment Curtailment [Member]
Pension and postretirement non-service income	0.0	0.2	0.8
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Total before tax	(3.5)	(3.6)	(5.5)
Income tax expense	1.0	0.9	1.4
Net of tax	(2.5)	(2.7)	(4.1)
Total before tax	(3.5)	(3.6)	(5.5)
Income tax expense	1.0	0.9	1.4
Net income attributable to Conagra Brands, Inc.	$ (2.5)	$ (2.7)	$ (4.1)