Debt - Outstanding Obligations (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	May 14, 2018	Jul. 31, 2017	Jun. 30, 2014
Gross Amount
Total	$ 318,202	$ 515,106	$ 522,223
Less current portion	215	197,748	205,973
Total long-term debt	317,987	317,358	316,250
Debt Discount and Issuance Costs
Total	(82,538)	(98,223)	(103,530)
Less current portion	0	(7,567)	(10,177)
Total long-term debt	(82,538)	(90,656)	(93,353)
Long-term Debt, Current Maturities [Abstract]
Carrying Amount	235,664	416,883	418,693
Current maturities of long-term debt, net	215	190,181	195,796
Total long-term debt	235,449	226,702	222,897
2019 Convertible Notes
Long-term Debt, Current Maturities [Abstract]
Stated interest rate						2.125%
2024 Convertible Notes
Long-term Debt, Current Maturities [Abstract]
Stated interest rate					2.875%
Other debt
Gross Amount
Total	0	0	3,482
Debt Discount and Issuance Costs
Total	0	0	0
Long-term Debt, Current Maturities [Abstract]
Carrying Amount	0	0	3,482
Senior Notes | 2019 Convertible Notes
Gross Amount
Total	0	195,000	195,000
Debt Discount and Issuance Costs
Total	0	(7,567)	(10,177)
Long-term Debt, Current Maturities [Abstract]
Carrying Amount	0	187,433	184,823
Senior Notes | 2019 Convertible Notes Embedded Derivative
Gross Amount
Total	0	2,552	7,491
Debt Discount and Issuance Costs
Total	0	0	0
Long-term Debt, Current Maturities [Abstract]
Carrying Amount	0	2,552	7,491
Senior Notes | 2024 Convertible Notes
Gross Amount
Total	143,750	143,750	143,750
Debt Discount and Issuance Costs
Total	(33,841)	(37,892)	(39,188)
Long-term Debt, Current Maturities [Abstract]
Carrying Amount	109,909	105,858	104,562
Senior Notes | 2025 Convertible Notes
Gross Amount
Total	172,500	172,500	172,500
Debt Discount and Issuance Costs
Total	(47,958)	(52,764)	(54,165)
Long-term Debt, Current Maturities [Abstract]
Carrying Amount	124,542	119,736	118,335
Stated interest rate				2.375%
Unsecured Debt | 8.5% unsecured debt due 2024
Gross Amount
Total	1,148	1,304	0
Debt Discount and Issuance Costs
Total	0	0	0
Long-term Debt, Current Maturities [Abstract]
Carrying Amount	$ 1,148	1,304	0
Stated interest rate	8.50%
Receivables Securitization Facility | CASHMAX secured borrowing facility
Gross Amount
Total	$ 804	0	0
Debt Discount and Issuance Costs
Total	(739)	0	0
Long-term Debt, Current Maturities [Abstract]
Carrying Amount	$ 65	$ 0	$ 0