Short-Term Investments (Details) (USD $)	3 Months Ended
	Dec. 28, 2013	Dec. 29, 2012	Sep. 28, 2013
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Cash and cash equivalent, Cost Basis	$ 138,375,000		$ 110,444,000
Cash and cash equivalent, Unrealized Gains	0		0
Cash and cash equivalent, Unrealized Losses	0		0
Cash and cash equivalent, Fair Value	138,375,000		110,444,000
Available-for-sale securities: Cost Basis	134,714,000		139,081,000
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments	602,000		601,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	(14,000)		(16,000)
Available-for-sale securities: Fair Value	135,302,000		139,666,000
Available-for-sale Securities, Debt Maturities [Abstract]
Due in less than 1 year, Amortized Cost	134,714,000		139,081,000
Due in less than 1 year, Estimated Fair Value	135,302,000		139,666,000
Proceeds from sale of available-for-sale securities	7,000,000	56,600,000
Maximum [Member]
Available-for-sale Securities, Debt Maturities [Abstract]
Realized gross gains from sale of available-for-sale securities	100,000	100,000
US Treasury and agency obligations
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Available-for-sale securities: Cost Basis	102,657,000		103,694,000
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments	544,000		507,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	(5,000)		(1,000)
Available-for-sale securities: Fair Value	103,196,000		104,200,000
Foreign Government Debt [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Available-for-sale securities: Cost Basis	5,024,000		5,040,000
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments	9,000		28,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	(4,000)		(5,000)
Available-for-sale securities: Fair Value	5,029,000		5,063,000
Corporate notes and obligations
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Available-for-sale securities: Cost Basis	19,035,000		20,352,000
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments	49,000		66,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	(5,000)		(10,000)
Available-for-sale securities: Fair Value	19,079,000		20,408,000
Commercial Paper [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Available-for-sale securities: Cost Basis	7,998,000		9,995,000
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments	0		0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0		0
Available-for-sale securities: Fair Value	$ 7,998,000		$ 9,995,000