SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Reclassifications From Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Feb. 23, 2020	Nov. 24, 2019	Aug. 25, 2019	Feb. 24, 2019	Nov. 25, 2018	Aug. 26, 2018	Feb. 23, 2020	Feb. 24, 2019
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Interest expense, net	$ (117.7)			$ (130.9)			$ (361.8)	$ (260.5)
Pension and postretirement non-service income	(16.4)			(9.8)			(37.2)	(29.7)
Income from continuing operations before income taxes and equity method investment earnings	263.2			297.1			731.7	635.5
Income tax expense	(68.9)			(67.2)			(141.5)	(147.0)
Net income attributable to Conagra Brands, Inc.	204.4	$ 260.5	$ 173.8	242.0	$ 131.6	$ 178.2	638.7	551.8
Reclassification out of accumulated other comprehensive loss | Cash flow hedges
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Interest expense, net	(0.9)			(0.9)			(2.5)	(1.1)
Income from continuing operations before income taxes and equity method investment earnings	(0.9)			(0.9)			(2.5)	(1.1)
Income tax expense	0.2			0.3			0.6	0.3
Net income attributable to Conagra Brands, Inc.	(0.7)			(0.6)			(1.9)	(0.8)
Reclassification out of accumulated other comprehensive loss | Net prior service cost
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Pension and postretirement non-service income	0.2			0.2			0.5	0.6
Reclassification out of accumulated other comprehensive loss | Net actuarial gain
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Pension and postretirement non-service income	(1.1)			(0.3)			(3.4)	(1.1)
Reclassification out of accumulated other comprehensive loss | Pension and postretirement liabilities
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Income from continuing operations before income taxes and equity method investment earnings	(2.8)			(0.1)			(4.2)	(0.5)
Income tax expense	0.6			0.0			1.0	0.1
Net income attributable to Conagra Brands, Inc.	(2.2)			(0.1)			(3.2)	(0.4)
Reclassification out of accumulated other comprehensive loss | Curtailment
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Pension and postretirement non-service income	0.2			0.0			0.8	0.0
Reclassification out of accumulated other comprehensive loss | Settlement
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Pension and postretirement non-service income	$ (2.1)			$ 0.0			$ (2.1)	$ 0.0