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. 30, 2012	Sep. 30, 2011
Investment Holdings [Line Items]
Amortized Cost	$ 823,518	$ 820,030
Unrealized Gains	1,443	1,632
Unrealized Losses	(56)	(546)
Estimated Fair Value	824,905	821,116
U.S. Agency Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	25,054	29,858
Unrealized Gains	38	65
Unrealized Losses	0	(4)
Estimated Fair Value	25,092	29,919
Municipal debt securities [Member]
Investment Holdings [Line Items]
Amortized Cost	388,574	471,005
Unrealized Gains	840	1,251
Unrealized Losses	(43)	(55)
Estimated Fair Value	389,371	472,201
Corporate Bonds [Member]
Investment Holdings [Line Items]
Amortized Cost	124,540	177,129
Unrealized Gains	565	316
Unrealized Losses	(13)	(487)
Estimated Fair Value	125,092	176,958
Money Market Funds [Member]
Investment Holdings [Line Items]
Amortized Cost	264,366	142,038
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	264,366	142,038
Commercial Paper [Member]
Investment Holdings [Line Items]
Amortized Cost	20,984
Unrealized Gains	0
Unrealized Losses	0
Estimated Fair Value	$ 20,984