SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Reclassifications from Accumulated Other Comprehensive Income (Loss) into Income (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Feb. 27, 2022	Nov. 28, 2021	Aug. 29, 2021	Feb. 28, 2021	Nov. 29, 2020	Aug. 30, 2020	Feb. 27, 2022	Feb. 28, 2021
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net	$ (94.6)			$ (100.6)			$ (283.7)	$ (322.0)
Pension and postretirement non-service income	(16.1)			(13.7)			(48.3)	(41.2)
Equity method investment earnings	48.1			21.5			97.8	51.0
Income before income taxes and equity method investment earnings	280.7			361.8			896.5	1,209.0
Income tax expense	(109.9)			(101.6)			(263.8)	(269.0)
Net income attributable to Conagra Brands, Inc.	218.4	$ 275.5	$ 235.4	281.4	$ 378.9	$ 329.0	729.3	989.3
Selling, general and administrative expenses	(338.0)			(309.7)			(993.5)	(967.7)
Reclassification out of accumulated other comprehensive loss | Cash flow hedges
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net	(0.8)			(0.8)			(2.3)	(2.4)
Equity method investment earnings	0.4			0.0			1.3	0.0
Income before income taxes and equity method investment earnings	(0.4)			(0.8)			(1.0)	(2.9)
Income tax expense	0.2			0.2			0.3	0.7
Net income attributable to Conagra Brands, Inc.	(0.2)			(0.6)			(0.7)	(2.2)
Selling, general and administrative expenses							0.0	(0.5)
Reclassification out of accumulated other comprehensive loss | Net actuarial gain
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Pension and postretirement non-service income	(0.9)			(0.8)			(2.7)	(2.6)
Reclassification out of accumulated other comprehensive loss | Pension and postretirement liabilities
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes and equity method investment earnings	(0.9)			(0.8)			(2.6)	(2.4)
Income tax expense	0.3			0.2			0.8	0.6
Net income attributable to Conagra Brands, Inc.	$ (0.6)			$ (0.6)			(1.8)	(1.8)
Reclassification out of accumulated other comprehensive loss | Net prior service cost
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Pension and postretirement non-service income							$ 0.1	$ 0.2