Investments (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Oct. 27, 2012	Oct. 29, 2011	Oct. 27, 2012	Oct. 29, 2011	Apr. 28, 2012
Schedule of Investments [Line Items]
Amount of investment which enhance return on cash	$ 24,800,000		$ 24,800,000
Gross Unrealized Gains			2,117,000		2,908,000
Gross Unrealized Losses			(144,000)		(90,000)
Fair Value	35,614,000		35,614,000		11,200,000
Sales of Available-for-sale Securities [Abstract]
Proceeds from sales	3,480,000	1,050,000	4,908,000	3,210,000
Gross realized gains	621,000	52,000	845,000	447,000
Gross realized losses	(10,000)	(24,000)	(36,000)	(27,000)
Available-for-sale fair value by contractual maturity [Abstract]
Available-for-sale securities, after one through five years, fair value	8,600,000		8,600,000
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	17,500,000		17,500,000
Available-for-sale securities, after five through ten years, fair value	800,000		800,000
Available-for-sale securities, after ten years, fair value	600,000		600,000
Other Long-Term Assets [Member]
Schedule of Investments [Line Items]
Available-for-sale investments	27,000,000		27,000,000		10,200,000
Trading securities					1,000,000
Other Current Assets [Member]
Schedule of Investments [Line Items]
Available-for-sale investments	8,600,000		8,600,000
Equity securities [Member]
Schedule of Investments [Line Items]
Gross Unrealized Gains			1,993,000		2,806,000
Gross Unrealized Losses			(134,000)		(83,000)
Fair Value	6,489,000		6,489,000		7,237,000
Fixed income [Member]
Schedule of Investments [Line Items]
Gross Unrealized Gains			124,000		102,000
Gross Unrealized Losses			(10,000)		(7,000)
Fair Value	27,515,000		27,515,000		2,850,000
Mutual funds [Member]
Schedule of Investments [Line Items]
Gross Unrealized Gains			0		0
Gross Unrealized Losses			0		0
Fair Value	1,071,000		1,071,000		950,000
Other [Member]
Schedule of Investments [Line Items]
Gross Unrealized Gains			0		0
Gross Unrealized Losses			0		0
Fair Value	$ 539,000		$ 539,000		$ 163,000