Composition Of Certain Financial Statement Captions (Schedule Of Investment Portfolio Recorded As Cash Equivalents, Short-Term Investments, And Long-Term Investments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 29, 2013	Sep. 28, 2012
Investment Holdings [Line Items]
Amortized Cost	$ 451,327	$ 686,609
Unrealized Gains	862	1,736
Unrealized Losses	(61)	(60)
Estimated Fair Value	452,128	688,285
U.S. Agency Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	53,723	24,997
Unrealized Gains	21	18
Unrealized Losses	(5)	(3)
Estimated Fair Value	53,739	25,012
Municipal debt securities [Member]
Investment Holdings [Line Items]
Amortized Cost	231,532	400,958
Unrealized Gains	398	728
Unrealized Losses	(44)	(38)
Estimated Fair Value	231,886	401,648
Commercial Paper [Member]
Investment Holdings [Line Items]
Amortized Cost	6,980	24,299
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	6,980	24,299
Corporate Bonds [Member]
Investment Holdings [Line Items]
Amortized Cost	156,325	219,265
Unrealized Gains	443	990
Unrealized Losses	(12)	(19)
Estimated Fair Value	156,756	220,236
Money Market Funds [Member]
Investment Holdings [Line Items]
Amortized Cost	2,767	17,090
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	$ 2,767	$ 17,090