Marketable Securities - Summary of Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,278,422	$ 3,679
Gross Unrealized Losses	(14,660)
Gross Unrealized Gains	22
Fair Value	1,263,784	3,679
U.S. Treasury securities and obligations of U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	804,774
Gross Unrealized Losses	(6,163)
Gross Unrealized Gains	21
Fair Value	798,632
Bank certificates of deposits
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,335	30
Gross Unrealized Losses	(158)
Gross Unrealized Gains	1
Fair Value	8,178	30
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	406,270	3,624
Gross Unrealized Losses	(8,113)
Fair Value	398,157	3,624
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	59,043
Gross Unrealized Losses	(226)
Fair Value	$ 58,817
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		25
Fair Value		$ 25

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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