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v3.22.2.2

Marketable Securities (Tables) | 12 Months Ended
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Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract] |
Summary of Amortized Cost and Fair Value, Including Accrued Interest Receivable and Unrealized Holding Gains (Losses) on Short-term and Long-term Marketable Securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Gross |  | Gross |  | ​
​ | ​ | Amortized | ​ | Unrealized | ​ | Unrealized | ​ | ​
​ | ​ | Cost | ​ | Losses | ​ | Gains | ​ | Fair Value
September 30, 2022: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
U.S. Treasury securities and obligations of U.S. government agencies |  | $ | 804,774 | ​ | $ | (6,163) | ​ | $ | 21 |  | $ | 798,632
Bank certificates of deposits | ​ | ​ | 8,335 | ​ | ​ | (158) | ​ | ​ | 1 | ​ | ​ | 8,178
Corporate securities | ​ | ​ | 406,270 | ​ | ​ | (8,113) | ​ | ​ | — | ​ | ​ | 398,157
Municipal securities |  | ​ | 59,043 | ​ | ​ | (226) | ​ | ​ | — |  | ​ | 58,817
​ | ​ | $ | 1,278,422 | ​ | $ | (14,660) | ​ | $ | 22 | ​ | $ | 1,263,784
September 30, 2021: | ​ | ​ |  | ​ |  |  | ​ |  |  | ​ |  |
Bank certificates of deposits | ​ | $ | 30 | ​ | $ | — | ​ | $ | — | ​ | $ | 30
Corporate securities | ​ | ​ | 3,624 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 3,624
Municipal securities | ​ |  | — | ​ | ​ | — | ​ | ​ | — |  | ​ | —
Other debt securities | ​ |  | 25 | ​ | ​ | — | ​ | ​ | — |  | ​ | 25
​ | ​ | $ | 3,679 | ​ | $ | — | ​ | $ | — | ​ | $ | 3,679
​
Fair Value of Marketable Securities by Contractual Maturity | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | Amortized | ​ | ​ | ​
​ |  | ​ | ​ | Cost | ​ | ​ | Fair Value
Due in one year or less | ​ | ​ | ​ | $ | 914,706 | ​ | $ | 909,913
Due after one year through five years | ​ | ​ | ​ |  | 360,930 | ​ |  | 351,085
Due after five years through ten years | ​ | ​ | ​ | ​ | — | ​ | ​ | —
Due after ten years | ​ | ​ | ​ |  | 2,786 | ​ |  | 2,786
Total marketable securities | ​ | ​ | ​ | $ | 1,278,422 | ​ | $ | 1,263,784
​

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- Definition Tabular disclosure of maturities of an entity's investments as well as any other information pertinent to the investments. + References No definition available. + Details
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- Definition Tabular disclosure of the reconciliation of available-for-sale securities from cost basis to fair value. + References No definition available. + Details
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