Short-Term Investments (Details) (USD $)	3 Months Ended		6 Months Ended					3 Months Ended		6 Months Ended
	Mar. 31, 2012	Apr. 02, 2011	Mar. 31, 2012	Apr. 02, 2011	Oct. 01, 2011	Mar. 31, 2012 Foreign Operations [Member]	Jan. 31, 2012 Foreign Operations [Member]	Mar. 31, 2012 Maximum [Member]	Apr. 02, 2011 Maximum [Member]	Mar. 31, 2012 Maximum [Member]	Apr. 02, 2011 Maximum [Member]	Mar. 31, 2012 Certificates of deposit	Oct. 01, 2011 Certificates of deposit	Mar. 31, 2012 US Treasury and agency obligations	Oct. 01, 2011 US Treasury and agency obligations	Mar. 31, 2012 Corporate notes and obligations	Oct. 01, 2011 Corporate notes and obligations	Mar. 31, 2012 Foreign Currencies [Member] Foreign Operations [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Cash and cash equivalent, Cost Basis	$ 86,030,000		$ 86,030,000		$ 166,931,000
Cash and cash equivalent, Unrealized Gains	34,000		34,000		131,000
Cash and cash equivalent, Unrealized Losses	0		0		(1,000)
Cash and cash equivalent, Fair Value	86,064,000		86,064,000		167,061,000
Available-for-sale securities: Cost Basis	128,429,000		128,429,000		52,883,000							2,000,000	6,500,000	85,220,000	1,101,000	41,209,000	45,282,000
Available-for-sale securities: Unrealized Gains	719,000		719,000		286,000							3,000	10,000	454,000	1,000	262,000	275,000
Available-for-sale securities: Unrealized Losses	(37,000)		(37,000)		(27,000)							0	0	(19,000)	(1,000)	(18,000)	(26,000)
Available-for-sale securities: Fair Value	129,111,000		129,111,000		53,142,000							2,003,000	6,510,000	85,655,000	1,101,000	41,453,000	45,531,000
Available-for-sale Securities, Debt Maturities [Abstract]
Due in less than 1 year, Amortized Cost	126,429,000		126,429,000		46,383,000
Due in less than 1 year, Estimated Fair Value	127,108,000		127,108,000		46,632,000
Total investments in available-for-sale debt securities, Amortized Cost	126,429,000		126,429,000		46,383,000
Total investments in available-for-sale debt securities, Estimated Fair Value	127,108,000		127,108,000		46,632,000									81,200,000		38,100,000
Proceeds from sale of available-for-sale securities	32,700,000	19,100,000	60,100,000	37,500,000
Realized gross gains from sale of available-for-sale securities								100,000	100,000	100,000	100,000
Gross unrealized losses on investments with unrealized losses that are deemed to be availble-for-sale securities			35,000
Cash, Cash Equivalents, and Short-term Investments						$ 149,300,000	$ 89,800,000											$ 54,800,000