XML 38 R28.htm IDEA: XBRL DOCUMENT
v3.24.1.u1

Marketable Securities (Tables) | 6 Months Ended
--- | ---
Mar. 31, 2024
Investments, Debt and Equity Securities [Abstract] |
Summary of amortized cost and fair value | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Gross |  | Gross |  | ​
​ | ​ | Amortized | ​ | Unrealized | ​ | Unrealized | ​ | ​
​ | ​ | Cost | ​ | Losses | ​ | Gains | ​ | Fair Value
March 31, 2024: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
U.S. Treasury securities and obligations of U.S. government agencies |  | $ | 433,188 | ​ | $ | (902) | ​ | $ | 8 |  | $ | 432,294
Bank certificates of deposit | ​ | ​ | 7,870 | ​ | ​ | (68) | ​ | ​ | — | ​ | ​ | 7,802
Corporate securities | ​ | ​ | 171,648 | ​ | ​ | (1,515) | ​ | ​ | 3 | ​ | ​ | 170,136
Municipal securities |  | ​ | 1,006 | ​ | ​ | — | ​ | ​ | — |  | ​ | 1,006
​ | ​ | $ | 613,712 | ​ | $ | (2,485) | ​ | $ | 11 | ​ | $ | 611,238
September 30, 2023: | ​ | ​ |  | ​ |  |  | ​ |  |  | ​ |  |
U.S. Treasury securities and obligations of U.S. government agencies | ​ | $ | 227,804 |  | $ | (2,573) |  | $ | — | ​ | $ | 225,231
Bank certificates of deposit | ​ | ​ | 8,122 | ​ | ​ | (170) | ​ | ​ | — | ​ | ​ | 7,952
Corporate securities | ​ | ​ | 221,155 | ​ | ​ | (4,127) | ​ | ​ | — | ​ | ​ | 217,028
​ | ​ | $ | 457,081 | ​ | $ | (6,870) | ​ | $ | — | ​ | $ | 450,211
Schedule of fair values of marketable securities by contractual maturities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Amortized | ​ | ​ | ​
​ | ​ | Cost | ​ | ​ | Fair Value
Due in one year or less | ​ | $ | 470,012 | ​ | $ | 468,220
Due after one year through five years | ​ |  | 140,222 | ​ |  | 139,540
Due after five years through ten years | ​ | ​ | — | ​ | ​ | —
Due after ten years | ​ |  | 3,478 | ​ |  | 3,478
Total marketable securities | ​ | $ | 613,712 | ​ | $ | 611,238

X
- 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
Name: | us-gaap_InvestmentsClassifiedByContractualMaturityDateTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the reconciliation of available-for-sale securities from cost basis to fair value. + References No definition available. + Details
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesReconciliationTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration