Pension and Postretirement Benefits - Components of Pension Benefit and Other Postretirement Benefit Costs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 25, 2012	Nov. 27, 2011	Nov. 25, 2012	Nov. 27, 2011
Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 0.1	$ 0.1	$ 0.2	$ 0.3
Interest cost	2.5	3.2	5.0	6.9
Amortization of prior service cost	(2.1)	(3.6)	(4.2)	(5.8)
Recognized net actuarial loss	1.5	2.0	3.0	3.5
Total benefit cost	2.0	1.7	4.0	4.9
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	20.1	17.1	40.3	34.2
Interest cost	36.6	37.2	73.2	74.4
Expected return on plan assets	(52.2)	(48.9)	(104.5)	(97.8)
Amortization of prior service cost	0.8	0.7	1.6	1.5
Curtailment loss			0.8
Benefit cost - Company plans	5.3	6.1	11.4	12.3
Pension benefit cost - multi-employer plans	2.2	2.8	4.3	4.9
Total benefit cost	$ 7.5	$ 8.9	$ 15.7	$ 17.2