PENSION AND POSTRETIREMENT BENEFITS - Components of Pension Benefit and Other Postretirement Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 24, 2019	Feb. 25, 2018	Feb. 24, 2019	Feb. 25, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Total benefit cost (benefit)	$ (5.7)	$ (17.4)	$ (16.1)	$ (33.2)
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Service cost	2.8	4.8	8.3	21.6
Interest cost	34.0	27.6	98.7	83.5
Expected return on plan assets	(44.6)	(50.3)	(130.1)	(150.0)
Amortization of prior service cost	0.7	0.7	2.1	2.1
Recognized net actuarial gain	0.0	0.0	0.0	3.4
Curtailment loss	0.0	0.0	0.0	0.7
Total benefit cost (benefit)	(7.1)	(17.2)	(21.0)	(38.7)
Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Service cost	0.0	0.0	0.1	0.0
Interest cost	1.0	1.0	2.9	2.8
Amortization of prior service cost	(0.5)	(0.9)	(1.5)	(2.5)
Recognized net actuarial gain	(0.4)	0.0	(1.2)	0.0
Curtailment loss	0.0	0.0	(0.6)	0.0
Total benefit cost (benefit)	0.1	0.1	(0.3)	0.3
Multi-employer plans | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Total benefit cost (benefit)	$ 1.4	$ (0.2)	$ 4.9	$ 5.5