PENSION AND POSTRETIREMENT BENEFITS (Costs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 22, 2015	Feb. 23, 2014	Feb. 22, 2015	Feb. 23, 2014
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 22.1	$ 22.3	$ 66.4	$ 66.8
Interest cost	40.4	37.7	121.1	113.3
Expected return on plan assets	(67.0)	(63.3)	(201.0)	(189.7)
Amortization of prior service cost	0.9	1.1	2.7	2.9
Special termination benefits	0	0	6.9	0
Benefit cost — Company plans	(3.6)	(2.2)	(3.9)	(6.7)
Pension benefit cost — multi-employer plans	2.8	2.7	9.5	9.4
Total benefit cost	(0.8)	0.5	5.6	2.7
Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.1	0.1	0.4	0.5
Interest cost	2.5	2.5	7.5	7.3
Amortization of prior service cost	(2.0)	(1.8)	(5.9)	(5.4)
Recognized net actuarial loss	0.9	1.6	2.6	5.0
Total benefit cost	$ 1.5	$ 2.4	$ 4.6	$ 7.4