STOCKHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Feb. 25, 2018	Feb. 26, 2017	Feb. 25, 2018	Feb. 26, 2017
Conagra Brands, Inc. Stockholders' Equity
Balance at beginning of period			$ 4,077.8
Stock option and incentive plans			40.2
Spinoff of Lamb Weston			14.8
Currency translation adjustment, net			24.9
Repurchase of common shares			(860.0)
Unrealized gain on securities	$ 0.6	$ 0.1	1.0	$ 0.4
Derivative adjustment, net			1.6
Activities of noncontrolling interests			2.7
Pension and postretirement healthcare benefits			26.6
Dividends declared on common stock; $0.6375 per share			$ (258.9)
Dividends declared on common stock (in dollars per share)			$ 0.6375
Net income attributable to Conagra Brands, Inc.	362.8	$ 179.7	$ 738.8	$ 488.0
Balance at ending of period	$ 3,809.5		3,809.5
Accounting Standards Update 2018-02
Conagra Brands, Inc. Stockholders' Equity
Adoption of ASU 2018-02			$ 0.0
Common Stock
Conagra Brands, Inc. Stockholders' Equity
Balance at beginning of period (in shares)			567.9
Balance at beginning of period			$ 2,839.7
Balance at end of period (in shares)	567.9		567.9
Balance at ending of period	$ 2,839.7		$ 2,839.7
Additional Paid-in Capital
Conagra Brands, Inc. Stockholders' Equity
Balance at beginning of period			1,171.9
Stock option and incentive plans			1.8
Balance at ending of period	1,173.7		1,173.7
Retained Earnings
Conagra Brands, Inc. Stockholders' Equity
Balance at beginning of period			4,247.0
Stock option and incentive plans			(0.3)
Spinoff of Lamb Weston			14.8
Dividends declared on common stock; $0.6375 per share			(258.9)
Balance at ending of period	4,758.8		4,758.8
Retained Earnings | Accounting Standards Update 2018-02
Conagra Brands, Inc. Stockholders' Equity
Adoption of ASU 2018-02			17.4
Accumulated Other Comprehensive Income (Loss)
Conagra Brands, Inc. Stockholders' Equity
Balance at beginning of period			(212.9)
Currency translation adjustment, net			25.6
Unrealized gain on securities			1.0
Derivative adjustment, net			1.6
Balance at ending of period	(175.5)		(175.5)
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2018-02
Conagra Brands, Inc. Stockholders' Equity
Adoption of ASU 2018-02			(17.4)
Treasury Stock
Conagra Brands, Inc. Stockholders' Equity
Balance at beginning of period			(4,054.9)
Stock option and incentive plans			38.7
Repurchase of common shares			(860.0)
Balance at ending of period	(4,876.2)		(4,876.2)
Noncontrolling Interests
Conagra Brands, Inc. Stockholders' Equity
Balance at beginning of period			87.0
Currency translation adjustment, net			(0.7)
Activities of noncontrolling interests			2.7
Balance at ending of period	$ 89.0		$ 89.0