Fair Value Measurements - Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018
Notes receivable from Grupo Finmart, net | Carrying Value
Financial assets:
Financial assets	$ 25,166	$ 37,425	$ 56,751
Notes receivable from Grupo Finmart, net | Estimated Fair Value
Financial assets:
Financial assets	26,601	41,153	65,091
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	26,601	41,153	65,091
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
Investment in unconsolidated affiliates | Carrying Value
Financial assets:
Financial assets	29,387	49,500	46,509
Investment in unconsolidated affiliates | Estimated Fair Value
Financial assets:
Financial assets	29,387	49,500	46,926
Investment in unconsolidated affiliates | Estimated Fair Value | Level 1
Financial assets:
Financial assets	26,611	49,500	46,926
Investment in unconsolidated affiliates | Estimated Fair Value | Level 2
Financial assets:
Financial assets	0	0	0
Investment in unconsolidated affiliates | Estimated Fair Value | Level 3
Financial assets:
Financial assets	2,776	0	0
2019 Convertible Notes | Carrying Value
Financial liabilities:
Financial liabilities	192,688	187,433	182,296
2019 Convertible Notes | Estimated Fair Value
Financial liabilities:
Financial liabilities	193,440	189,150	206,856
2019 Convertible Notes | Estimated Fair Value | Level 1
Financial liabilities:
Financial liabilities	0	0	0
2019 Convertible Notes | Estimated Fair Value | Level 2
Financial liabilities:
Financial liabilities	193,440	189,150	206,856
2019 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Financial liabilities	0	0	0
2024 Convertible Notes | Carrying Value
Financial liabilities:
Financial liabilities	108,533	105,858	103,287
2024 Convertible Notes | Estimated Fair Value
Financial liabilities:
Financial liabilities	159,994	180,399	212,060
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	159,994	180,399	212,060
2024 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Financial liabilities	0	0
2025 Convertible Notes | Carrying Value
Financial liabilities:
Financial liabilities	122,918	119,736
2025 Convertible Notes | Estimated Fair Value
Financial liabilities:
Financial liabilities	151,179	161,253
2025 Convertible Notes | Estimated Fair Value | Level 1
Financial liabilities:
Financial liabilities	0	0
2025 Convertible Notes | Estimated Fair Value | Level 2
Financial liabilities:
Financial liabilities	151,179	161,253
2025 Convertible Notes | Estimated Fair Value | Level 3
Financial liabilities:
Financial liabilities	$ 0	0
8.5% unsecured notes due 2024
Financial liabilities:
Stated interest rate	8.50%
8.5% unsecured notes due 2024 | Carrying Value
Financial liabilities:
Financial liabilities	$ 1,191	1,304
8.5% unsecured notes due 2024 | Estimated Fair Value
Financial liabilities:
Financial liabilities	1,191	1,304
8.5% unsecured notes due 2024 | Estimated Fair Value | Level 1
Financial liabilities:
Financial liabilities	0	0
8.5% unsecured notes due 2024 | Estimated Fair Value | Level 2
Financial liabilities:
Financial liabilities	0	0
8.5% unsecured notes due 2024 | Estimated Fair Value | Level 3
Financial liabilities:
Financial liabilities	1,191	$ 1,304
CASHMAX secured borrowing facility | Carrying Value
Financial liabilities:
Financial liabilities	304
CASHMAX secured borrowing facility | Estimated Fair Value
Financial liabilities:
Financial liabilities	1,105
CASHMAX secured borrowing facility | Estimated Fair Value | Level 1
Financial liabilities:
Financial liabilities	0
CASHMAX secured borrowing facility | Estimated Fair Value | Level 2
Financial liabilities:
Financial liabilities	0
CASHMAX secured borrowing facility | Estimated Fair Value | Level 3
Financial liabilities:
Financial liabilities	$ 1,105