Marketable Securities (Amortized Cost and Fair Value of Marketable Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 58,793	$ 57,317
Gross unrealized gains		146
Gross unrealized losses		(28)
Fair value	59,099	57,435
Corporate notes/bonds
Debt Securities, Available-for-sale [Line Items]
Amortized cost	58,793	56,318
Gross unrealized gains	323	146
Gross unrealized losses	(17)	(28)
Fair value	$ 59,099	56,436
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized cost		999
Gross unrealized gains		0
Gross unrealized losses		0
Fair value		$ 999

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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