Composition Of Certain Financial Statement Captions (Schedule Of Cash, Cash Equivalents, And Investments) (Details) (USD $)																	6 Months Ended
	Mar. 29, 2013	Sep. 28, 2012	Mar. 29, 2013 Municipal Notes [Member]		Sep. 28, 2012 Municipal Notes [Member]		Mar. 29, 2013 Agency Securities [Member]		Sep. 28, 2012 Agency Securities [Member]		Mar. 29, 2013 Commercial Paper [Member]	Sep. 28, 2012 Commercial Paper [Member]	Mar. 29, 2013 Corporate Bonds [Member]		Sep. 28, 2012 Corporate Bonds [Member]		Mar. 29, 2013 Minimum [Member]	Mar. 29, 2013 Maximum [Member]
Composition Of Certain Financial Statement Captions [Line Items]
Cash	$ 325,741,000	$ 468,622,000
Cash equivalents			0		2,003,000						0	4,885,000
Cash and cash equivalents	328,508,000	492,600,000
Short-term investments	124,415,000	302,693,000	56,477,000		172,037,000		6,902,000		3,999,000		6,980,000	19,414,000	54,056,000		107,243,000
Long-term investments	327,946,000	361,614,000	175,409,000	[1]	227,608,000	[1]	46,837,000	[1]	21,013,000	[1]			102,700,000	[1]	112,993,000	[1]
Total cash, cash equivalents and investments	780,869,000	1,156,907,000
Cost method investments	$ 3,000,000
Long-term investments, Maturities																	1 year	3 years

[1] Our long-term investments have maturities that range from one to three years.