Pensions and Other Postretirement Benefits (Details) (USD $)	9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Jan. 27, 2013	Apr. 29, 2012	Jan. 27, 2013 Pension Benefits [Member]	Jan. 25, 2012 Pension Benefits [Member]	Jan. 27, 2013 Pension Benefits [Member]	Jan. 25, 2012 Pension Benefits [Member]	Jan. 27, 2013 Other Retiree Benefits [Member]	Jan. 25, 2012 Other Retiree Benefits [Member]	Jan. 27, 2013 Other Retiree Benefits [Member]	Jan. 25, 2012 Other Retiree Benefits [Member]	Jan. 27, 2013 Maximum [Member]
Components of net periodic benefit cost
Service cost			$ 7,990,000	$ 8,262,000	$ 23,793,000	$ 25,318,000	$ 1,628,000	$ 1,478,000	$ 4,875,000	$ 4,475,000
Interest cost			33,503,000	34,273,000	99,756,000	104,759,000	2,487,000	2,844,000	7,452,000	8,591,000
Expected return on assets			(63,500,000)	(57,665,000)	(189,130,000)	(176,202,000)	0	0	0	0
Amortization of prior service cost/(credit)			639,000	493,000	1,912,000	1,486,000	(1,544,000)	(1,533,000)	(4,633,000)	(4,595,000)
Amortization of unrecognized loss			19,151,000	20,691,000	57,235,000	62,857,000	451,000	274,000	1,352,000	821,000
Settlements			3,116,000	0	4,463,000	0	0	0	0	0
Net periodic benefit (income)/expense			899,000	6,054,000	(1,971,000)	18,218,000	3,022,000	3,063,000	9,046,000	9,292,000
Pensions and Other Post-Retirement Benefits (Textuals) [Abstract]
Benefit obligation recognized for pension benefits as other non-current assets	492,400,000	399,900,000
Employer contribution	53,000,000
Defined Benefit plan, Expected full year combined cash contributions											$ 75,000,000