Short-Term And Long-Term Investments (Schedule Of Short-Term And Long-Term Investments) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Schedule of Investments [Line Items]
Cost or Amortized Cost	$ 847,176
Fair Value	846,794
Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	363,569	352,193
Gross Unrealized Gains	354	285
Gross Unrealized Losses	(46)	(28)
Fair Value	363,877	352,450
Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	483,607	729,348
Gross Unrealized Gains	309	744
Gross Unrealized Losses	(999)	(1,111)
Fair Value	482,917	728,981
Corporate Bonds And Notes [Member] | Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	205,490	125,010
Gross Unrealized Gains	244	210
Gross Unrealized Losses	(36)	(8)
Fair Value	205,698	125,212
Corporate Bonds And Notes [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	325,896	260,345
Gross Unrealized Gains	208	363
Gross Unrealized Losses	(822)	(390)
Fair Value	325,282	260,318
Municipal Bonds And Notes [Member] | Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	43,398	72,116
Gross Unrealized Gains	34	58
Gross Unrealized Losses	(2)	(10)
Fair Value	43,430	72,164
Municipal Bonds And Notes [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	24,559	24,332
Gross Unrealized Gains	31	44
Gross Unrealized Losses	(8)	(5)
Fair Value	24,582	24,371
US Government Debt Securities [Member] | Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	4,996	4,998
Gross Unrealized Gains	10	2
Gross Unrealized Losses	0	0
Fair Value	5,006	5,000
US Government Debt Securities [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	7,377	14,755
Gross Unrealized Gains	30	43
Gross Unrealized Losses	0	0
Fair Value	7,407	14,798
Auction Rate Securities [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost		3,300
Gross Unrealized Gains		0
Gross Unrealized Losses		(264)
Fair Value		3,036
U.S. Government Agency Securities [Member] | Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	109,685	150,069
Gross Unrealized Gains	66	15
Gross Unrealized Losses	(8)	(10)
Fair Value	109,743	150,074
U.S. Government Agency Securities [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	123,207	426,616
Gross Unrealized Gains	40	294
Gross Unrealized Losses	(160)	(452)
Fair Value	123,087	426,458
Foreign Government Debt Securities [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	2,568
Gross Unrealized Gains	0
Gross Unrealized Losses	(9)
Fair Value	$ 2,559