Investments - Summary of Short-term, Long-term Investments and Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Sep. 30, 2022
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Short-term investments, Held to maturity, Adjusted Bases	$ 299,582	$ 268,391
Short-term investments, Held to maturity, Gross Unrealized Gains	0	0
Short-term investments, Held to maturity, Gross Unrealized Losses	(2,644)	(3,661)
Short-term investments, Held to maturity, Fair Value	296,938	264,730
Long-term investments, Held to maturity, Adjusted Basis	115,774	105,872
Long-term investments, Held to maturity, Gross Unrealized Gains	0	0
Long-term investments, Held to maturity, Gross Unrealized Losses	(4,440)	(5,569)
Long-term investments, Held to maturity, Fair Value	111,334	100,303
Debt securities
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Short-term investments, Held to maturity, Adjusted Bases	299,582	218,391
Short-term investments, Held to maturity, Gross Unrealized Gains	0	0
Short-term investments, Held to maturity, Gross Unrealized Losses	(2,644)	(3,661)
Short-term investments, Held to maturity, Fair Value	296,938	214,730
Long-term investments, Held to maturity, Adjusted Basis	115,774	105,872
Long-term investments, Held to maturity, Gross Unrealized Gains	0	0
Long-term investments, Held to maturity, Gross Unrealized Losses	(4,440)	(5,569)
Long-term investments, Held to maturity, Fair Value	111,334	100,303
Certificate of deposits
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Short-term investments, Held to maturity, Adjusted Bases	0	50,000
Short-term investments, Held to maturity, Gross Unrealized Gains	0	0
Short-term investments, Held to maturity, Gross Unrealized Losses	0	0
Short-term investments, Held to maturity, Fair Value	$ 0	$ 50,000