Fair Value of Financial Instruments - Narrative (Detail) (Short-term investments [Member], USD $)	Oct. 27, 2013	Apr. 28, 2013	Oct. 28, 2012
Short-term investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term bond funds	$ 6,200,000	$ 5,300,000	$ 5,200,000
Unrealized gain (loss) on short-term bond funds	$ (59,000)	$ 54,000	$ 60,000