Investments - Summary of Investments by Type of Security (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Debt Securities, Available-for-sale [Line Items]
Cost	$ 18,051	$ 8,472
Gross Unrealized Gains	4	0
Gross Unrealized Losses	(1)	(24)
Fair Market Value	18,054	8,448
US Treasury \| Short-term
Debt Securities, Available-for-sale [Line Items]
Cost	4,240	3,693
Gross Unrealized Gains	2	0
Gross Unrealized Losses	0	(10)
Fair Market Value	4,242	3,683
US Treasury \| Long-term
Debt Securities, Available-for-sale [Line Items]
Cost	1,102
Gross Unrealized Gains	0
Gross Unrealized Losses	(1)
Fair Market Value	1,101
Corporate debt securities \| Short-term
Debt Securities, Available-for-sale [Line Items]
Cost	12,258	4,779
Gross Unrealized Gains	2	0
Gross Unrealized Losses	0	(14)
Fair Market Value	12,260	$ 4,765
Corporate debt securities \| Long-term
Debt Securities, Available-for-sale [Line Items]
Cost	451
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Market Value	$ 451

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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