SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Reclassifications from Accumulated Other Comprehensive Loss into Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May 26, 2019	Feb. 24, 2019	Nov. 25, 2018	Aug. 26, 2018	May 27, 2018	Feb. 25, 2018	Nov. 26, 2017	Aug. 27, 2017	May 26, 2019	May 27, 2018	May 28, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense, net									$ (391.4)	$ (158.7)	$ (195.5)
Pension and postretirement non-service income									(35.1)	(80.4)	(55.2)
Selling, general and administrative expenses									1,473.4	1,398.4	1,474.0
Total before tax									899.1	972.1	800.7
Income tax expense									(218.8)	(174.6)	(254.7)
Net income attributable to Conagra Brands, Inc.	$ 126.5	$ 242.0	$ 131.6	$ 178.2	$ 69.6	$ 362.8	$ 223.5	$ 152.5	678.3	808.4	639.3
Reclassification out of Accumulated Other Comprehensive Income | Cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense, net									(1.9)	0.1	(0.2)
Total before tax									(1.9)	0.1	(0.2)
Income tax expense									0.5	0.0	0.1
Net income attributable to Conagra Brands, Inc.									(1.4)	0.1	(0.1)
Reclassification out of Accumulated Other Comprehensive Income | Net prior service cost (benefit)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Pension and postretirement non-service income									0.9	(0.4)	(3.9)
Reclassification out of Accumulated Other Comprehensive Income | Net actuarial loss (gain)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Pension and postretirement non-service income									(1.4)	0.0	0.5
Reclassification out of Accumulated Other Comprehensive Income | Amortization of pension and postretirement healthcare liabilities:
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total before tax									(1.5)	0.9	10.4
Income tax expense									0.4	(0.2)	(4.0)
Net income attributable to Conagra Brands, Inc.									(1.1)	0.7	6.4
Reclassification out of Accumulated Other Comprehensive Income | Currency translation losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Selling, general and administrative expenses									10.4	0.0	0.0
Total before tax									10.4	0.0	0.0
Income tax expense									0.0	0.0	0.0
Net income attributable to Conagra Brands, Inc.									10.4	0.0	0.0
Pension Benefits | Reclassification out of Accumulated Other Comprehensive Income | Pension and Postretirement healthcare settlement
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Pension and postretirement non-service income									0.0	1.3	13.8
Postretirement Healthcare | Reclassification out of Accumulated Other Comprehensive Income | Pension and Postretirement healthcare settlement
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Pension and postretirement non-service income									$ (1.0)	$ 0.0	$ 0.0