Components of Pension Benefit and Other Postretirement Benefit Costs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Aug. 26, 2012	Aug. 28, 2011
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 20.2	$ 17.1
Interest cost	36.6	37.2
Expected return on plan assets	(52.3)	(48.9)
Amortization of prior service cost (gain)	0.8	0.8
Curtailment loss	0.8
Benefit cost - Company plans	6.1	6.2
Pension benefit cost - multi-employer plans	2.1	2.1
Total benefit cost	8.2	8.3
Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.1	0.2
Interest cost	2.5	3.7
Amortization of prior service cost (gain)	(2.1)	(2.2)
Recognized net actuarial loss	1.5	1.5
Benefit cost - Company plans	2.0	3.2
Total benefit cost	$ 2.0	$ 3.2