Fair Value Measurements - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2019	Apr. 30, 2019
Promissory note receivable due April 2024
Financial assets:
Notes receivable				$ 1,100	$ 1,100
Promissory note receivable due April 2024 | Carrying Value
Financial assets:
Notes receivable		$ 1,251
Promissory note receivable due April 2024 | Estimated Fair Value
Financial assets:
Notes receivable		1,251
Promissory note receivable due April 2024 | Estimated Fair Value | Level 1
Financial assets:
Notes receivable		0
Promissory note receivable due April 2024 | Estimated Fair Value | Level 2
Financial assets:
Notes receivable		0
Promissory note receivable due April 2024 | Estimated Fair Value | Level 3
Financial assets:
Notes receivable		1,251
Promissory note receivable from Founders
Financial assets:
Notes receivable			$ 15,000
Promissory note receivable from Founders | Carrying Value
Financial assets:
Notes receivable	$ 15,722	16,500
Promissory note receivable from Founders | Estimated Fair Value
Financial assets:
Notes receivable	15,722	16,500
Promissory note receivable from Founders | Estimated Fair Value | Level 1
Financial assets:
Notes receivable	0	0
Promissory note receivable from Founders | Estimated Fair Value | Level 2
Financial assets:
Notes receivable	0	0
Promissory note receivable from Founders | Estimated Fair Value | Level 3
Financial assets:
Notes receivable	15,722	16,500
Investments in unconsolidated affiliates | Carrying Value
Financial assets:
Investments in unconsolidated affiliates	13,329	10,987
Investments in unconsolidated affiliates | Estimated Fair Value
Financial assets:
Investments in unconsolidated affiliates	42,496	35,998
Investments in unconsolidated affiliates | Estimated Fair Value | Level 1
Financial assets:
Investments in unconsolidated affiliates	41,646	35,998
Investments in unconsolidated affiliates | Estimated Fair Value | Level 2
Financial assets:
Investments in unconsolidated affiliates	0	0
Investments in unconsolidated affiliates | Estimated Fair Value | Level 3
Financial assets:
Investments in unconsolidated affiliates	850	0
2024 Convertible Notes | Carrying Value
Financial liabilities:
Debt instrument, fair value		34,265
2024 Convertible Notes | Estimated Fair Value
Financial liabilities:
Debt instrument, fair value		35,765
2024 Convertible Notes | Estimated Fair Value | Level 1
Financial liabilities:
Debt instrument, fair value		0
2024 Convertible Notes | Estimated Fair Value | Level 2
Financial liabilities:
Debt instrument, fair value		35,765
2024 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Debt instrument, fair value		0
2025 Convertible Notes | Carrying Value
Financial liabilities:
Debt instrument, fair value	103,072	102,563
2025 Convertible Notes | Estimated Fair Value
Financial liabilities:
Debt instrument, fair value	100,401	96,137
2025 Convertible Notes | Estimated Fair Value | Level 1
Financial liabilities:
Debt instrument, fair value	0	0
2025 Convertible Notes | Estimated Fair Value | Level 2
Financial liabilities:
Debt instrument, fair value	100,401	96,137
2025 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Debt instrument, fair value	0	0
2029 Convertible Notes | Carrying Value
Financial liabilities:
Debt instrument, fair value	224,256	223,284
2029 Convertible Notes | Estimated Fair Value
Financial liabilities:
Debt instrument, fair value	273,700	224,112
2029 Convertible Notes | Estimated Fair Value | Level 1
Financial liabilities:
Debt instrument, fair value	0	0
2029 Convertible Notes | Estimated Fair Value | Level 2
Financial liabilities:
Debt instrument, fair value	273,700	224,112
2029 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Debt instrument, fair value	$ 0	$ 0