Fair Value Measurements - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Sep. 30, 2024	Jun. 30, 2024	Sep. 30, 2023
Promissory note receivable from Founders
Financial assets:
Notes receivable, fair value				$ 15,000
Promissory note receivable from Founders \| Carrying Value
Financial assets:
Notes receivable, fair value	$ 17,525	$ 15,722	$ 16,186
Promissory note receivable from Founders \| Estimated Fair Value
Financial assets:
Notes receivable, fair value	17,525	15,722	16,186
Promissory note receivable from Founders \| Estimated Fair Value \| Level 1
Financial assets:
Notes receivable, fair value	0	0	0
Promissory note receivable from Founders \| Estimated Fair Value \| Level 2
Financial assets:
Notes receivable, fair value	0	0	0
Promissory note receivable from Founders \| Estimated Fair Value \| Level 3
Financial assets:
Notes receivable, fair value	17,525	15,722	16,186
Investments in unconsolidated affiliates \| Carrying Value
Financial assets:
Investments in unconsolidated affiliates	13,753	13,329	12,297
Investments in unconsolidated affiliates \| Estimated Fair Value
Financial assets:
Investments in unconsolidated affiliates	50,657	42,496	40,762
Investments in unconsolidated affiliates \| Estimated Fair Value \| Level 1
Financial assets:
Investments in unconsolidated affiliates	49,807	41,646	39,912
Investments in unconsolidated affiliates \| Estimated Fair Value \| Level 2
Financial assets:
Investments in unconsolidated affiliates	0	0	0
Investments in unconsolidated affiliates \| Estimated Fair Value \| Level 3
Financial assets:
Investments in unconsolidated affiliates	850	850	850
2024 Convertible Notes \| Carrying Value
Financial liabilities:
Debt instruments, fair value			34,386
2024 Convertible Notes \| Estimated Fair Value
Financial liabilities:
Debt instruments, fair value			34,690
2024 Convertible Notes \| Estimated Fair Value \| Level 1
Financial liabilities:
Debt instruments, fair value			0
2024 Convertible Notes \| Estimated Fair Value \| Level 2
Financial liabilities:
Debt instruments, fair value			34,690
2024 Convertible Notes \| Estimated Fair Value \| Level 3
Financial liabilities:
Debt instruments, fair value			0
2025 Convertible Notes \| Carrying Value
Financial liabilities:
Debt instruments, fair value		103,072	102,940
2025 Convertible Notes \| Estimated Fair Value
Financial liabilities:
Debt instruments, fair value		100,401	99,238
2025 Convertible Notes \| Estimated Fair Value \| Level 1
Financial liabilities:
Debt instruments, fair value		0	0
2025 Convertible Notes \| Estimated Fair Value \| Level 2
Financial liabilities:
Debt instruments, fair value		100,401	99,238
2025 Convertible Notes \| Estimated Fair Value \| Level 3
Financial liabilities:
Debt instruments, fair value		0	0
2029 Convertible Notes \| Carrying Value
Financial liabilities:
Debt instruments, fair value	224,982	224,256	223,998
2029 Convertible Notes \| Estimated Fair Value
Financial liabilities:
Debt instruments, fair value	330,050	273,700	262,564
2029 Convertible Notes \| Estimated Fair Value \| Level 1
Financial liabilities:
Debt instruments, fair value	0	0	0
2029 Convertible Notes \| Estimated Fair Value \| Level 2
Financial liabilities:
Debt instruments, fair value	330,050	273,700	262,564
2029 Convertible Notes \| Estimated Fair Value \| Level 3
Financial liabilities:
Debt instruments, fair value	0	$ 0	$ 0
2032 Senior Notes \| Carrying Value
Financial liabilities:
Debt instruments, fair value	292,619
2032 Senior Notes \| Estimated Fair Value
Financial liabilities:
Debt instruments, fair value	316,406
2032 Senior Notes \| Estimated Fair Value \| Level 1
Financial liabilities:
Debt instruments, fair value	0
2032 Senior Notes \| Estimated Fair Value \| Level 2
Financial liabilities:
Debt instruments, fair value	316,406
2032 Senior Notes \| Estimated Fair Value \| Level 3
Financial liabilities:
Debt instruments, fair value	$ 0