Fair Value Measurements - Financial Assets, Temporary Equity and Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Jul. 31, 2017	Jun. 30, 2014
Financial assets:
Notes receivable from Grupo Finmart, net		$ 7,182	$ 34,199
Investments in unconsolidated affiliates		34,516	49,500
Carrying Value
Financial assets:
Notes receivable from Grupo Finmart, net		7,182	37,425
Investments in unconsolidated affiliates		34,516	49,500
Estimate of Fair Value Measurement
Financial assets:
Notes receivable from Grupo Finmart, net		7,582	41,153
Investments in unconsolidated affiliates		28,308	49,500
Estimate of Fair Value Measurement | Level 1
Financial assets:
Notes receivable from Grupo Finmart, net		0	0
Investments in unconsolidated affiliates		20,252	49,500
Estimate of Fair Value Measurement | Level 2
Financial assets:
Notes receivable from Grupo Finmart, net		0	0
Investments in unconsolidated affiliates		0	0
Estimate of Fair Value Measurement | Level 3
Financial assets:
Notes receivable from Grupo Finmart, net		7,582	41,153
Investments in unconsolidated affiliates		8,056	0
2019 Convertible Notes
Financial liabilities:
Stated interest rate					2.125%
2019 Convertible Notes | Carrying Value
Financial liabilities:
Convertible promissory note			187,433
2019 Convertible Notes | Estimate of Fair Value Measurement
Financial liabilities:
Convertible promissory note			189,150
2019 Convertible Notes | Estimate of Fair Value Measurement | Level 1
Financial liabilities:
Convertible promissory note			0
2019 Convertible Notes | Estimate of Fair Value Measurement | Level 2
Financial liabilities:
Convertible promissory note			189,150
2019 Convertible Notes | Estimate of Fair Value Measurement | Level 3
Financial liabilities:
Convertible promissory note			0
2024 Convertible Notes
Financial liabilities:
Stated interest rate				2.875%
2024 Convertible Notes | Carrying Value
Financial liabilities:
Convertible promissory note		111,311	105,858
2024 Convertible Notes | Estimate of Fair Value Measurement
Financial liabilities:
Convertible promissory note		139,969	180,399
2024 Convertible Notes | Estimate of Fair Value Measurement | Level 1
Financial liabilities:
Convertible promissory note		0	0
2024 Convertible Notes | Estimate of Fair Value Measurement | Level 2
Financial liabilities:
Convertible promissory note		139,969	180,399
2024 Convertible Notes | Estimate of Fair Value Measurement | Level 3
Financial liabilities:
Convertible promissory note		0	0
2025 Convertible Notes | Carrying Value
Financial liabilities:
Convertible promissory note		126,210	119,736
2025 Convertible Notes | Estimate of Fair Value Measurement
Financial liabilities:
Convertible promissory note		138,345	161,253
2025 Convertible Notes | Estimate of Fair Value Measurement | Level 1
Financial liabilities:
Convertible promissory note		0	0
2025 Convertible Notes | Estimate of Fair Value Measurement | Level 2
Financial liabilities:
Convertible promissory note		138,345	161,253
2025 Convertible Notes | Estimate of Fair Value Measurement | Level 3
Financial liabilities:
Convertible promissory note		0	0
8.5% unsecured debt due 2024 | Carrying Value
Financial liabilities:
Convertible promissory note		$ 1,092	1,304
Stated interest rate		8.50%
8.5% unsecured debt due 2024 | Estimate of Fair Value Measurement
Financial liabilities:
Convertible promissory note		$ 1,092	1,304
8.5% unsecured debt due 2024 | Estimate of Fair Value Measurement | Level 1
Financial liabilities:
Convertible promissory note		0
8.5% unsecured debt due 2024 | Estimate of Fair Value Measurement | Level 2
Financial liabilities:
Convertible promissory note		0
8.5% unsecured debt due 2024 | Estimate of Fair Value Measurement | Level 3
Financial liabilities:
Convertible promissory note		$ 1,092	$ 1,304
Secured Promissory Note 2.89%, Due 2024
Financial liabilities:
Notes receivable, interest rate	2.89%	2.89%
Secured Promissory Note 2.89%, Due 2024 | Carrying Value
Financial assets:
2.89% promissory note receivable due April 2024		$ 1,117
Secured Promissory Note 2.89%, Due 2024 | Estimate of Fair Value Measurement
Financial assets:
2.89% promissory note receivable due April 2024		1,117
Secured Promissory Note 2.89%, Due 2024 | Estimate of Fair Value Measurement | Level 1
Financial assets:
2.89% promissory note receivable due April 2024		0
Secured Promissory Note 2.89%, Due 2024 | Estimate of Fair Value Measurement | Level 2
Financial assets:
2.89% promissory note receivable due April 2024		0
Secured Promissory Note 2.89%, Due 2024 | Estimate of Fair Value Measurement | Level 3
Financial assets:
2.89% promissory note receivable due April 2024		1,117
CASHMAX secured borrowing facility | Carrying Value
Financial liabilities:
CASHMAX secured borrowing facility		634
CASHMAX secured borrowing facility | Estimate of Fair Value Measurement
Financial liabilities:
CASHMAX secured borrowing facility		634
CASHMAX secured borrowing facility | Estimate of Fair Value Measurement | Level 1
Financial liabilities:
CASHMAX secured borrowing facility		0
CASHMAX secured borrowing facility | Estimate of Fair Value Measurement | Level 2
Financial liabilities:
CASHMAX secured borrowing facility		0
CASHMAX secured borrowing facility | Estimate of Fair Value Measurement | Level 3
Financial liabilities:
CASHMAX secured borrowing facility		$ 634