Pension and Postretirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Feb. 26, 2012	Feb. 27, 2011	Feb. 26, 2012	Feb. 27, 2011	May 27, 2012	Sep. 08, 2011	May 29, 2011
Pension Benefits [Member]
Components of pension benefit and other postretirement benefit costs
Service cost	$ 17.2	$ 14.9	$ 51.4	$ 44.7
Interest cost	37.2	36.8	111.6	110.6
Expected return on plan assets	(44.9)	(43.2)	(134.7)	(129.8)
Amortization of prior service cost	0.8	0.8	2.3	2.4
Curtailment loss		0.1		1.4
Recognized net actuarial loss	9.6	4.1	28.9	12.3
Benefit cost - Company plans	19.9	13.5	59.5	41.6
Pension benefit cost - multi-employer plans	1.7	2.5	6.6	7.6
Total benefit cost	21.6	16.0	66.1	49.2
Pension and Postretirement Benefits (Textual) [Abstract]
Employer contributions to pension plan and other postretirement plan	5.5		77.0
Further contribution to pension and other postretirement plan.			10.6
Postretirement Benefits [Member]
Components of pension benefit and other postretirement benefit costs
Service cost	0.1	0.2	0.4	0.5
Interest cost	3.1	4.0	10.0	12.1
Expected return on plan assets				(0.1)
Amortization of prior service cost	(3.9)	(2.5)	(9.7)	(7.2)
Recognized net actuarial loss	2.1	1.2	5.6	3.5
Total benefit cost	1.4	2.9	6.3	8.8
Pension and Postretirement Benefits (Textual) [Abstract]
Employer contributions to pension plan and other postretirement plan	9.0		26.5
Further contribution to pension and other postretirement plan.			5.0
Calculated gains as a result of remeasurement recognized as a credit to other comprehensive income	27.6		27.6
Discount rate						4.30%	4.90%
Reduction in net expense related to benefit retirement plan					$ 5.2