Short-Term And Long-Term Investments (Schedule Of Short-Term And Long-Term Investments) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Schedule of Investments [Line Items]
Cost or Amortized Cost	$ 1,081,541
Fair Value	1,081,431
Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	352,193	320,457
Gross Unrealized Gains	285	563
Gross Unrealized Losses	(28)	(50)
Fair Value	352,450	320,970
Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	729,348	661,557
Gross Unrealized Gains	744	1,602
Gross Unrealized Losses	(1,111)	(356)
Fair Value	728,981	662,803
Certificates of Deposit [Member] | Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost		3,528
Gross Unrealized Gains		5
Gross Unrealized Losses		0
Fair Value		3,533
Corporate Bonds And Notes [Member] | Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	125,010	193,548
Gross Unrealized Gains	210	482
Gross Unrealized Losses	(8)	(40)
Fair Value	125,212	193,990
Corporate Bonds And Notes [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	260,345	228,438
Gross Unrealized Gains	363	1,063
Gross Unrealized Losses	(390)	(60)
Fair Value	260,318	229,441
Municipal Bonds And Notes [Member] | Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	72,116	63,371
Gross Unrealized Gains	58	61
Gross Unrealized Losses	(10)	(10)
Fair Value	72,164	63,422
Municipal Bonds And Notes [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	24,332	30,177
Gross Unrealized Gains	44	138
Gross Unrealized Losses	(5)	(8)
Fair Value	24,371	30,307
US Government Debt Securities [Member] | Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	4,998
Gross Unrealized Gains	2
Gross Unrealized Losses	0
Fair Value	5,000
US Government Debt Securities [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	14,755	4,983
Gross Unrealized Gains	43	12
Gross Unrealized Losses	0	0
Fair Value	14,798	4,995
Auction Rate Securities [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	3,300	5,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(264)	(250)
Fair Value	3,036	4,750
U.S. Government Agency Securities [Member] | Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	150,069	60,010
Gross Unrealized Gains	15	15
Gross Unrealized Losses	(10)	0
Fair Value	150,074	60,025
U.S. Government Agency Securities [Member] | Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	426,616	392,959
Gross Unrealized Gains	294	389
Gross Unrealized Losses	(452)	(38)
Fair Value	$ 426,458	$ 393,310