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	Dec. 28, 2012	Sep. 28, 2012
Investment Holdings [Line Items]
Amortized Cost	$ 451,020	$ 686,609
Unrealized Gains	776	1,736
Unrealized Losses	(203)	(60)
Estimated Fair Value	451,593	688,285
U.S. Agency Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	56,403	24,997
Unrealized Gains	10	18
Unrealized Losses	(2)	(3)
Estimated Fair Value	56,411	25,012
Municipal debt securities [Member]
Investment Holdings [Line Items]
Amortized Cost	217,715	400,958
Unrealized Gains	323	728
Unrealized Losses	(121)	(38)
Estimated Fair Value	217,917	401,648
Commercial Paper [Member]
Investment Holdings [Line Items]
Amortized Cost	11,024	24,299
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	11,024	24,299
Corporate Bonds [Member]
Investment Holdings [Line Items]
Amortized Cost	156,637	219,265
Unrealized Gains	443	990
Unrealized Losses	(80)	(19)
Estimated Fair Value	157,000	220,236
Money Market Funds [Member]
Investment Holdings [Line Items]
Amortized Cost	9,241	17,090
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	$ 9,241	$ 17,090