Debt - Outstanding Obligations (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	May 14, 2018	Jul. 31, 2017
Gross Amount
Total	$ 317,543	$ 317,976	$ 318,202
Less current portion	268	214	215
Total long-term debt	317,275	317,762	317,987
Debt Discount and Issuance Costs
Total	(69,657)	(79,382)	(82,538)
Less current portion	0	0	0
Total long-term debt	(69,657)	(79,382)	(82,538)
Carrying Amount
Total	247,886	238,594	235,664
Less current portion	268	214	215
Total long-term debt	247,618	238,380	235,449
2024 Convertible Notes
Carrying Amount
Stated interest rate					2.875%
Senior Notes | 2024 Convertible Notes
Gross Amount
Total	143,750	143,750	143,750
Debt Discount and Issuance Costs
Total	(28,069)	(32,439)	(33,841)
Carrying Amount
Total	115,681	111,311	109,909
Senior Notes | 2025 Convertible Notes
Gross Amount
Total	172,500	172,500	172,500
Debt Discount and Issuance Costs
Total	(41,122)	(46,290)	(47,958)
Carrying Amount
Total	131,378	126,210	124,542
Stated interest rate				2.375%
Unsecured Debt | 8.5% unsecured debt due 2024
Gross Amount
Total	998	1,092	1,148
Debt Discount and Issuance Costs
Total	0	0	0
Carrying Amount
Total	$ 998	1,092	1,148
Stated interest rate	8.50%
Receivables Securitization Facility | CASHMAX secured borrowing facility
Gross Amount
Total	$ 295	634	804
Debt Discount and Issuance Costs
Total	(466)	(653)	(739)
Carrying Amount
Total	$ (171)	$ (19)	$ 65