STOCKHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Feb. 26, 2017	Feb. 28, 2016	Feb. 26, 2017	Feb. 28, 2016	May 29, 2016
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period			$ 3,794.8
Stock option and incentive plans			100.8
Adoption of ASU 2016-09					$ (3.9)
Spinoff of Lamb Weston			788.8
Currency translation adjustment, net			(23.3)
Repurchase of common shares			(619.4)
Unrealized gain on securities	$ 0.1	$ (0.1)	0.4	$ 0.0
Derivative adjustment, net			(1.2)
Activities of noncontrolling interests			0.5
Pension and postretirement healthcare benefits			84.1
Dividends declared on common stock; $0.70 per share			$ (305.4)
Dividends declared on common stock (in dollars per share)			$ 0.70
Net income attributable to Conagra Brands, Inc.	179.7	$ 204.6	$ 488.0	$ (794.6)
Balance at ending of period	$ 4,304.2		$ 4,304.2
Common Stock
Increase (Decrease) in 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
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period			1,136.3
Stock option and incentive plans			29.8
Activities of noncontrolling interests			(0.8)
Balance at ending of period	1,165.3		1,165.3
Retained Earnings
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period			3,218.3
Stock option and incentive plans			(1.2)
Adoption of ASU 2016-09					$ (3.9)
Spinoff of Lamb Weston			775.2
Dividends declared on common stock; $0.70 per share			(305.4)
Net income attributable to Conagra Brands, Inc.			488.0
Balance at ending of period	4,171.0		4,171.0
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period			(344.5)
Spinoff of Lamb Weston			13.6
Currency translation adjustment, net			(23.7)
Unrealized gain on securities			0.4
Derivative adjustment, net			(1.2)
Pension and postretirement healthcare benefits			84.1
Balance at ending of period	(271.3)		(271.3)
Treasury Stock
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period			(3,136.2)
Stock option and incentive plans			72.2
Repurchase of common shares			(619.4)
Balance at ending of period	(3,683.4)		(3,683.4)
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period			81.2
Currency translation adjustment, net			0.4
Activities of noncontrolling interests			1.3
Balance at ending of period	$ 82.9		$ 82.9