Pensions and Other Postretirement Benefits (Details) (USD $)	6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Oct. 28, 2012	Apr. 29, 2012	Oct. 28, 2012 Pension Benefits [Member]	Oct. 26, 2011 Pension Benefits [Member]	Oct. 28, 2012 Pension Benefits [Member]	Oct. 26, 2011 Pension Benefits [Member]	Oct. 28, 2012 Other Retiree Benefits [Member]	Oct. 26, 2011 Other Retiree Benefits [Member]	Oct. 28, 2012 Other Retiree Benefits [Member]	Oct. 26, 2011 Other Retiree Benefits [Member]	Oct. 28, 2012 Maximum [Member]
Components of net periodic benefit cost
Service cost			$ 7,968,000	$ 8,445,000	$ 15,803,000	$ 17,056,000	$ 1,633,000	$ 1,489,000	$ 3,247,000	$ 2,997,000
Interest cost			33,371,000	34,939,000	66,253,000	70,486,000	2,492,000	2,860,000	4,965,000	5,747,000
Expected return on assets			(63,290,000)	(58,756,000)	(125,630,000)	(118,537,000)	0	0	0	0
Amortization of prior service cost/(credit)			641,000	495,000	1,273,000	993,000	(1,544,000)	(1,532,000)	(3,089,000)	(3,062,000)
Amortization of unrecognized loss			19,180,000	20,937,000	38,084,000	42,166,000	450,000	274,000	901,000	547,000
Settlements			333,000	0	1,347,000	0	0	0	0	0
Net periodic benefit (income)/expense			(1,797,000)	6,060,000	(2,870,000)	12,164,000	3,031,000	3,091,000	6,024,000	6,229,000
Pensions and Other Post-Retirement Benefits (Textuals) [Abstract]
Benefit obligation recognized for pension benefits as other non-current assets	462,300,000	399,900,000
Employer contribution	32,000,000
Defined Benefit plan, Expected full year combined cash contributions											$ 80,000,000