Summary Of Significant Accounting Policies (Marketable Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 15,494
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	31,287
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	46,781
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	43
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	102
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	145
Amortized cost	50,458	$ 49,738
Gross unrealized gains	2	0
Gross unrealized losses	(145)	(122)
Fair value	50,315	49,616
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Amortized Cost Basis	18,274	18,585
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	18,244	18,549
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Amortized Cost Basis	32,184	31,153
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	32,071	31,067
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	240
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	240
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	0
Amortized cost	240	681
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	240	681
Commercial Paper[Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost		11,945
Gross unrealized gains		0
Gross unrealized losses		(20)
Fair value		11,925
Corporate notes/bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	15,254
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	28,885
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	44,139
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	43
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	97
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	140
Amortized cost	47,811	34,701
Gross unrealized gains	2	0
Gross unrealized losses	(140)	(100)
Fair value	47,673	34,601
US Government Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,402
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,402
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	5
Amortized cost	2,407	2,411
Gross unrealized gains	0	0
Gross unrealized losses	(5)	(2)
Fair value	$ 2,402	$ 2,409