Investments - Summary of Investments by Type of Security (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Schedule Of Available For Sale Securities [Line Items]
Cost	$ 25,500	$ 18,051
Gross Unrealized Gains	100	4
Gross Unrealized Losses	(36)	(1)
Fair Market Value	25,564	18,054
Short-term investments \| U.S. Treasury
Schedule Of Available For Sale Securities [Line Items]
Cost	6,235	4,240
Gross Unrealized Gains	76	2
Gross Unrealized Losses	0	0
Fair Market Value	6,311	4,242
Short-term investments \| Asset-backed securities
Schedule Of Available For Sale Securities [Line Items]
Cost	1,657
Gross Unrealized Gains	2
Gross Unrealized Losses	0
Fair Market Value	1,659
Short-term investments \| Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Cost	11,063	12,258
Gross Unrealized Gains	1	2
Gross Unrealized Losses	(16)	0
Fair Market Value	11,048	12,260
Long-term investments \| U.S. Treasury
Schedule Of Available For Sale Securities [Line Items]
Cost	1,006	1,102
Gross Unrealized Gains	17	0
Gross Unrealized Losses	0	(1)
Fair Market Value	1,023	1,101
Long-term investments \| Asset-backed securities
Schedule Of Available For Sale Securities [Line Items]
Cost	3,086
Gross Unrealized Gains	0
Gross Unrealized Losses	(6)
Fair Market Value	3,080
Long-term investments \| Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Cost	2,453	451
Gross Unrealized Gains	4	0
Gross Unrealized Losses	(14)	0
Fair Market Value	$ 2,443	$ 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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