Fair Value Measurements - Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019
Notes receivable from Grupo Finmart, net | Carrying Value
Financial assets:
Notes receivable, fair value	$ 3,866	$ 7,182	$ 18,744
Notes receivable from Grupo Finmart, net | Estimated Fair Value
Financial assets:
Notes receivable, fair value	3,945	7,582	19,517
Notes receivable from Grupo Finmart, net | Estimated Fair Value | Level 1
Financial assets:
Notes receivable, fair value	0	0	0
Notes receivable from Grupo Finmart, net | Estimated Fair Value | Level 2
Financial assets:
Notes receivable, fair value	0	0	0
Notes receivable from Grupo Finmart, net | Estimated Fair Value | Level 3
Financial assets:
Notes receivable, fair value	$ 3,945	7,582	19,517
Zero-coupon convertible promissory note due January 2021 | Carrying Value
Financial assets:
Notes receivable, fair value			7,226
Zero-coupon convertible promissory note due January 2021 | Estimated Fair Value
Financial assets:
Notes receivable, fair value			7,226
Zero-coupon convertible promissory note due January 2021 | Estimated Fair Value | Level 1
Financial assets:
Notes receivable, fair value			0
Zero-coupon convertible promissory note due January 2021 | Estimated Fair Value | Level 2
Financial assets:
Notes receivable, fair value			0
Zero-coupon convertible promissory note due January 2021 | Estimated Fair Value | Level 3
Financial assets:
Notes receivable, fair value			7,226
2.89% promissory note receivable due April 2024
Financial liabilities:
Interest on note receivable	2.89%
2.89% promissory note receivable due April 2024 | Carrying Value
Financial assets:
Notes receivable, fair value	$ 1,140	1,117	1,108
2.89% promissory note receivable due April 2024 | Estimated Fair Value
Financial assets:
Notes receivable, fair value	1,140	1,117	1,108
2.89% promissory note receivable due April 2024 | Estimated Fair Value | Level 1
Financial assets:
Notes receivable, fair value	0	0	0
2.89% promissory note receivable due April 2024 | Estimated Fair Value | Level 2
Financial assets:
Notes receivable, fair value	0	0	0
2.89% promissory note receivable due April 2024 | Estimated Fair Value | Level 3
Financial assets:
Notes receivable, fair value	1,140	1,117	1,108
Investments in unconsolidated affiliates | Carrying Value
Financial assets:
Investments in unconsolidated affiliates, fair value	29,483	34,516	30,922
Investments in unconsolidated affiliates | Estimated Fair Value
Financial assets:
Investments in unconsolidated affiliates, fair value	33,602	28,308	27,158
Investments in unconsolidated affiliates | Estimated Fair Value | Level 1
Financial assets:
Investments in unconsolidated affiliates, fair value	25,779	20,252	24,464
Investments in unconsolidated affiliates | Estimated Fair Value | Level 2
Financial assets:
Investments in unconsolidated affiliates, fair value	0	0	0
Investments in unconsolidated affiliates | Estimated Fair Value | Level 3
Financial assets:
Investments in unconsolidated affiliates, fair value	7,823	8,056	2,694
2024 Convertible Notes | Carrying Value
Financial liabilities:
Debt instruments, fair value	115,681	111,311	109,909
2024 Convertible Notes | Estimated Fair Value
Financial liabilities:
Debt instruments, fair value	130,669	139,969	161,719
2024 Convertible Notes | Estimated Fair Value | Level 1
Financial liabilities:
Debt instruments, fair value	0	0	0
2024 Convertible Notes | Estimated Fair Value | Level 2
Financial liabilities:
Debt instruments, fair value	130,669	139,969	161,719
2024 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Debt instruments, fair value	0	0	0
2025 Convertible Notes | Carrying Value
Financial liabilities:
Debt instruments, fair value	131,378	126,210	124,542
2025 Convertible Notes | Estimated Fair Value
Financial liabilities:
Debt instruments, fair value	125,235	138,345	159,873
2025 Convertible Notes | Estimated Fair Value | Level 1
Financial liabilities:
Debt instruments, fair value	0	0	0
2025 Convertible Notes | Estimated Fair Value | Level 2
Financial liabilities:
Debt instruments, fair value	125,235	138,345	159,873
2025 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Debt instruments, fair value	$ 0	0	0
8.5% unsecured debt due 2024
Financial liabilities:
Stated interest rate	8.50%
8.5% unsecured debt due 2024 | Carrying Value
Financial liabilities:
Debt instruments, fair value	$ 998	1,092	1,148
8.5% unsecured debt due 2024 | Estimated Fair Value
Financial liabilities:
Debt instruments, fair value	998	1,092	1,148
8.5% unsecured debt due 2024 | Estimated Fair Value | Level 1
Financial liabilities:
Debt instruments, fair value	0	0	0
8.5% unsecured debt due 2024 | Estimated Fair Value | Level 2
Financial liabilities:
Debt instruments, fair value	0	0	0
8.5% unsecured debt due 2024 | Estimated Fair Value | Level 3
Financial liabilities:
Debt instruments, fair value	998	1,092	1,148
CASHMAX secured borrowing facility | Carrying Value
Financial liabilities:
Debt instruments, fair value	(171)	(19)	65
CASHMAX secured borrowing facility | Estimated Fair Value
Financial liabilities:
Debt instruments, fair value	295	634	804
CASHMAX secured borrowing facility | Estimated Fair Value | Level 1
Financial liabilities:
Debt instruments, fair value	0	0	0
CASHMAX secured borrowing facility | Estimated Fair Value | Level 2
Financial liabilities:
Debt instruments, fair value	0	0	0
CASHMAX secured borrowing facility | Estimated Fair Value | Level 3
Financial liabilities:
Debt instruments, fair value	$ 295	$ 634	$ 804