Consolidated Statements of Common Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Noncontrolling Interests
Beginning balance (in shares) at May. 31, 2015		567.9
Beginning balance at May. 31, 2015	$ 4,610.0	$ 2,839.7	$ 1,049.4	$ 4,331.1	$ (329.5)	$ (3,364.7)	$ 84.0
Increase (Decrease) in Stockholders' Equity
Stock option and incentive plans	319.0		91.7	(1.2)		228.5
Currency translation adjustment, net	14.5				18.7		(4.2)
Unrealized gain on securities	0.1				0.1
Derivative adjustment, net of reclassification adjustment	(1.3)				(1.3)
Activities of noncontrolling interests	(3.4)		(4.8)				1.4
Pension and postretirement healthcare benefits	(32.5)				(32.5)
Dividends declared on common stock	(434.6)			(434.6)
Net (loss) income attributable to Conagra Brands, Inc.	(677.0)			(677.0)
Ending balance (in shares) at May. 29, 2016		567.9
Ending balance at May. 29, 2016	3,794.8	$ 2,839.7	1,136.3	3,218.3	(344.5)	(3,136.2)	81.2
Increase (Decrease) in Stockholders' Equity
Adoption of ASU	(3.9)			(3.9)
Stock option and incentive plans	116.4		36.4	(1.3)		81.3
Spinoff of Lamb Weston	796.9			783.3	13.6
Currency translation adjustment, net	(13.4)				(16.6)		3.2
Repurchase of common shares	(1,000.0)					(1,000.0)
Unrealized gain on securities	0.3				0.3
Derivative adjustment, net of reclassification adjustment	(0.7)				(0.7)
Activities of noncontrolling interests	1.8		(0.8)				2.6
Pension and postretirement healthcare benefits	135.0				135.0
Dividends declared on common stock	(388.7)			(388.7)
Net (loss) income attributable to Conagra Brands, Inc.	639.3			639.3
Ending balance (in shares) at May. 28, 2017		567.9
Ending balance at May. 28, 2017	4,077.8	$ 2,839.7	1,171.9	4,247.0	(212.9)	(4,054.9)	87.0
Increase (Decrease) in Stockholders' Equity
Adoption of ASU	0.0			17.4	(17.4)
Stock option and incentive plans	53.7		10.0	(0.8)		44.3	0.2
Spinoff of Lamb Weston	14.8			14.8
Currency translation adjustment, net	0.7				4.6		(3.9)
Repurchase of common shares	(967.3)					(967.3)
Unrealized gain on securities	0.8				0.8
Derivative adjustment, net of reclassification adjustment	2.1				2.1
Activities of noncontrolling interests	(5.5)		(1.9)		(0.7)		(2.9)
Pension and postretirement healthcare benefits	113.0				113.0
Dividends declared on common stock	(341.9)			(341.9)
Net (loss) income attributable to Conagra Brands, Inc.	808.4			808.4
Ending balance (in shares) at May. 27, 2018		567.9
Ending balance at May. 27, 2018	$ 3,756.6	$ 2,839.7	$ 1,180.0	$ 4,744.9	$ (110.5)	$ (4,977.9)	$ 80.4