Marketable Securities (Summary of Individual Securities In Continuous Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 24,286
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(71)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		31,665
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		(342)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		55,951
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(413)
Certificates of Deposit [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		219
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		219
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(1)
Corporate notes/bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 12,419	24,067
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(14)	(70)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	16,369	30,670
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(14)	(333)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	28,788	54,737
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (28)	(403)
US Government Agencies Securities [Member]
Debt Securities, Available-for-sale [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, Less than 12 Months, Accumulated Loss		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		995
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		(9)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		995
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ (9)