Investments - Summary of Investments by Type of Security (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Schedule Of Available For Sale Securities [Line Items]
Cost	$ 5,862	$ 8,472
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(24)
Fair Market Value	5,861	8,448
Short-term investments \| U.S. Treasury
Schedule Of Available For Sale Securities [Line Items]
Cost		3,693
Gross Unrealized Gains		0
Gross Unrealized Losses		(10)
Fair Market Value		3,683
Short-term investments \| Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Cost	5,862	4,779
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(14)
Fair Market Value	$ 5,861	$ 4,765

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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Amount 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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