Investments - Summary of Investments by Type of Security (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Cost	$ 41,890	$ 18,051
Gross Unrealized Gains	111	4
Gross Unrealized Losses	(3)	(1)
Fair Market Value	41,998	18,054
US Treasury \| Short-term
Debt Securities, Available-for-sale [Line Items]
Cost	10,245	4,240
Gross Unrealized Gains	38	2
Gross Unrealized Losses	0	0
Fair Market Value	10,283	4,242
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
Asset-backed securities \| Short-term
Debt Securities, Available-for-sale [Line Items]
Cost	4,723
Gross Unrealized Gains	36
Gross Unrealized Losses	0
Fair Market Value	4,759
Corporate debt securities \| Short-term
Debt Securities, Available-for-sale [Line Items]
Cost	24,956	12,258
Gross Unrealized Gains	37	2
Gross Unrealized Losses	0	0
Fair Market Value	24,993	12,260
Corporate debt securities \| Long-term
Debt Securities, Available-for-sale [Line Items]
Cost	1,966	451
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(3)	0
Fair Market Value	$ 1,963	$ 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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