Merchandise Inventories - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Jan. 25, 2014	Jan. 26, 2013	Jan. 25, 2014	Jan. 26, 2013
Inventory [Line Items]
LIFO inventory adjustments	$ (3,934)	$ 308	$ (4,508)	$ 1,525

The difference between the change in the inventory reserve representing the cumulative difference in cost between the first in, first out and the last in, first out inventory valuation methods and any LIFO decrement which have been reflected in the statement of income during the period.

No definition available.

Name:	us-gaap_InventoryLIFOReserveEffectOnIncomeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration