Marketable Securities - Fair Value of Available-for-Sale Marketable Securities by Type of Security (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Sep. 30, 2022
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 201,477	$ 237,863
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2,291)	(3,340)
Fair Value	199,186	234,523
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	63,407	78,663
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,739)	(2,252)
Fair Value	61,668	76,411
U.S. Treasury Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	59,121	92,416
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(552)	(1,088)
Fair Value	58,569	91,328
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	78,949	66,784
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 78,949	$ 66,784

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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