Fair Value Measurements - Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019
Notes receivable from Grupo Finmart, net | Carrying Value
Financial assets:
Financial assets	$ 3,728	$ 7,182	$ 25,166
Notes receivable from Grupo Finmart, net | Estimated Fair Value
Financial assets:
Financial assets	3,853	7,582	26,601
Notes receivable from Grupo Finmart, net | Estimated Fair Value | Level 1
Financial assets:
Financial assets	0	0	0
Notes receivable from Grupo Finmart, net | Estimated Fair Value | Level 2
Financial assets:
Financial assets	0	0	0
Notes receivable from Grupo Finmart, net | Estimated Fair Value | Level 3
Financial assets:
Financial assets	$ 3,853	7,582	26,601
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:
Financial assets	$ 1,132	1,117
2.89% promissory note receivable due April 2024 | Estimated Fair Value
Financial assets:
Financial assets	1,132	1,117
2.89% promissory note receivable due April 2024 | Estimated Fair Value | Level 1
Financial assets:
Financial assets	0	0
2.89% promissory note receivable due April 2024 | Estimated Fair Value | Level 2
Financial assets:
Financial assets	0	0
2.89% promissory note receivable due April 2024 | Estimated Fair Value | Level 3
Financial assets:
Financial assets	1,132	1,117
Zero-coupon convertible promissory note due January 2021 | Carrying Value
Financial assets:
Financial assets			6,793
Zero-coupon convertible promissory note due January 2021 | Estimated Fair Value
Financial assets:
Financial assets			6,793
Zero-coupon convertible promissory note due January 2021 | Estimated Fair Value | Level 1
Financial assets:
Financial assets			0
Zero-coupon convertible promissory note due January 2021 | Estimated Fair Value | Level 2
Financial assets:
Financial assets			0
Zero-coupon convertible promissory note due January 2021 | Estimated Fair Value | Level 3
Financial assets:
Financial assets			6,793
Investments in unconsolidated affiliates | Carrying Value
Financial assets:
Financial assets	27,993	34,516	29,387
Investments in unconsolidated affiliates | Estimated Fair Value
Financial assets:
Financial assets	27,513	28,308	29,387
Investments in unconsolidated affiliates | Estimated Fair Value | Level 1
Financial assets:
Financial assets	19,734	20,252	26,611
Investments in unconsolidated affiliates | Estimated Fair Value | Level 2
Financial assets:
Financial assets	0	0	0
Investments in unconsolidated affiliates | Estimated Fair Value | Level 3
Financial assets:
Financial assets	7,779	8,056	2,776
2019 Convertible Notes | Carrying Value
Financial liabilities:
Financial liabilities			192,688
2019 Convertible Notes | Estimated Fair Value
Financial liabilities:
Financial liabilities			193,440
2019 Convertible Notes | Estimated Fair Value | Level 1
Financial liabilities:
Financial liabilities			0
2019 Convertible Notes | Estimated Fair Value | Level 2
Financial liabilities:
Financial liabilities			193,440
2019 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Financial liabilities			0
2024 Convertible Notes | Carrying Value
Financial liabilities:
Financial liabilities	114,196	111,311	108,533
2024 Convertible Notes | Estimated Fair Value
Financial liabilities:
Financial liabilities	106,203	139,969	159,994
2024 Convertible Notes | Estimated Fair Value | Level 1
Financial liabilities:
Financial liabilities	0	0	0
2024 Convertible Notes | Estimated Fair Value | Level 2
Financial liabilities:
Financial liabilities	106,203	139,969	159,994
2024 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Financial liabilities	0	0	0
2025 Convertible Notes | Carrying Value
Financial liabilities:
Financial liabilities	129,624	126,210	122,918
2025 Convertible Notes | Estimated Fair Value
Financial liabilities:
Financial liabilities	128,081	138,345	151,179
2025 Convertible Notes | Estimated Fair Value | Level 1
Financial liabilities:
Financial liabilities	0	0	0
2025 Convertible Notes | Estimated Fair Value | Level 2
Financial liabilities:
Financial liabilities	128,081	138,345	151,179
2025 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Financial liabilities	$ 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:
Financial liabilities	$ 983	1,092	1,191
8.5% unsecured debt due 2024 | Estimated Fair Value
Financial liabilities:
Financial liabilities	983	1,092	1,191
8.5% unsecured debt due 2024 | Estimated Fair Value | Level 1
Financial liabilities:
Financial liabilities	0	0	0
8.5% unsecured debt due 2024 | Estimated Fair Value | Level 2
Financial liabilities:
Financial liabilities	0	0	0
8.5% unsecured debt due 2024 | Estimated Fair Value | Level 3
Financial liabilities:
Financial liabilities	983	1,092	1,191
CASHMAX secured borrowing facility | Carrying Value
Financial liabilities:
Financial liabilities	(248)	(19)	304
CASHMAX secured borrowing facility | Estimated Fair Value
Financial liabilities:
Financial liabilities	281	634	1,105
CASHMAX secured borrowing facility | Estimated Fair Value | Level 1
Financial liabilities:
Financial liabilities	0	0	0
CASHMAX secured borrowing facility | Estimated Fair Value | Level 2
Financial liabilities:
Financial liabilities	0	0	0
CASHMAX secured borrowing facility | Estimated Fair Value | Level 3
Financial liabilities:
Financial liabilities	$ 281	$ 634	$ 1,105