PENSION AND POSTRETIREMENT BENEFITS - Schedule of Other Changes in Plan Assets and Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2020	May 26, 2019	May 27, 2018
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Net amount recognized	$ 43.2	$ (34.0)	$ 113.0
Pension Benefits
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial gain (loss)	21.9	(72.1)
Amendments	0.0	(1.4)
Amortization of prior service cost (benefit)	2.7	3.1
Settlement and curtailment gain	(1.3)	0.0
Recognized net actuarial loss (gain)	44.8	5.1
Net amount recognized	68.1	(65.3)
Other Benefits
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial gain (loss)	(2.9)	25.1
Amendments	0.0	0.8
Amortization of prior service cost (benefit)	(2.1)	(2.2)
Settlement and curtailment gain	(0.2)	(1.6)
Recognized net actuarial loss (gain)	(4.6)	(1.4)
Net amount recognized	$ (9.8)	$ 20.7