Investments (Tables)

12 Months Ended

Sep. 30, 2023

Investments, Debt and Equity Securities [Abstract]

Summary of Short-term, Long-term Investments and Marketable Securities

The Company’s investments consisted of the following:

	As of September 30, 2023
	(in thousands)
	Adjusted Basis		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Available-for-sale debt securities	$	295,699	$	—	$	(2,964)	$	292,735
Total current investments	$	295,699	$	—	$	(2,964)	$	292,735

The Company does not believe that the available-for-sale debt securities that were in an unrealized loss position have any credit loss impairment as of September 30, 2023.

	As of September 30, 2022
	(in thousands)
	Adjusted Basis		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Short-term investments (due within one year)
Held-to-maturity debt securities	$	218,391	$	—	$	(3,661)	$	214,730
Held-to-maturity certificate of deposit	50,000		—		—		50,000
Total current investments	$	268,391	$	—	$	(3,661)	$	264,730
Long-term investments (Due within one through three years)
Held-to-maturity debt securities	$	105,872	$	—	$	(5,569)	$	100,303
Total long-term investments	$	105,872	$	—	$	(5,569)	$	100,303