Pensions and Other Postretirement Benefits (Details) (USD $)	3 Months Ended		3 Months Ended
	Jul. 27, 2011	Apr. 27, 2011	Jul. 27, 2011 Pension Benefits [Member]	Jul. 28, 2010 Pension Benefits [Member]	Jul. 27, 2011 Other Retiree Benefits [Member]	Jul. 28, 2010 Other Retiree Benefits [Member]
Components of net periodic benefit cost
Service cost			$ 8,611,000	$ 7,737,000	$ 1,508,000	$ 1,561,000
Interest cost			35,547,000	34,279,000	2,887,000	3,154,000
Expected return on assets			(59,781,000)	(55,292,000)	0	0
Amortization of prior service cost/(credit)			498,000	591,000	(1,530,000)	(1,290,000)
Amortization of unrecognized loss			21,229,000	18,968,000	273,000	401,000
Net periodic benefit cost			6,104,000	6,283,000	3,138,000	3,826,000
Pensions and Other Post-Retirement Benefits (Textuals) [Abstract]
Benefit obligation recognized for pension benefits as other non-current assets	654,900,000	644,600,000
Employer contribution	$ 3,000,000
Defined Benefit plan, Expected full year combined cash contributions	less than 40 million