Short-Term Investments (Details) - USD ($) $ in Thousands		3 Months Ended
		Jan. 02, 2016	Dec. 27, 2014	Oct. 03, 2015
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Cash and cash equivalent, Cost Basis		$ 142,343		$ 130,607
Cash and cash equivalent, Unrealized Gains		0		0
Cash and cash equivalent, Unrealized Losses		0		0
Cash and cash equivalent, Fair Value		142,343		130,607
Available-for-sale securities: Cost Basis		191,506		192,609
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		2,585		2,301
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax		(260)		(2)
Available-for-sale securities: Fair Value		193,831		194,908
Available-for-sale Securities, Debt Maturities [Abstract]
Due in less than 1 year, Amortized Cost		140,303		148,088
Due in less than 1 year, Estimated Fair Value		140,835		149,100
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	[1]	35,934		29,252
Proceeds from sale of available-for-sale securities		15,100	$ 29,600
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	[1]	35,952		29,330
Maximum [Member]
Available-for-sale Securities, Debt Maturities [Abstract]
Realized gross gains from sale of available-for-sale securities		100	$ 100
US Treasury and agency obligations
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Available-for-sale securities: Cost Basis		146,996		149,708
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		706		1,040
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax		(215)		0
Available-for-sale securities: Fair Value		147,487		150,748
Corporate notes and obligations
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Available-for-sale securities: Cost Basis		19,744		17,892
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		104		52
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax		(45)		(2)
Available-for-sale securities: Fair Value		19,803		17,942
Equity Securities [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Available-for-sale securities: Cost Basis		15,269		15,269
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		1,775		1,209
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax		0		0
Available-for-sale securities: Fair Value		17,044		16,478
Commercial Paper [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Available-for-sale securities: Cost Basis		9,497		9,740
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		0		0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax		0		0
Available-for-sale securities: Fair Value		$ 9,497		$ 9,740

[1] lassified as short-term investments because these securities are highly liquid and can be sold at any time.