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Pension And Other Postretirement Benefit Plans - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 9 Months Ended
Jan. 26, 2013
Jan. 28, 2012
Jan. 26, 2013
Jan. 28, 2012
Pension and Other Postretirement Benefit Plans [Line Items]        
Pension expense $ 751 $ 504 $ 2,338 $ 1,608
Company contributions for postretirement plan $ 38 $ 38 $ 113 $ 113