Long-Term Debt - Summary of Maturities of Borrowing Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
2021	$ 3,125
2022	6,250
2023	10,938
2024	12,500
2025	262,500
Total before unamortized discount and issuance costs and current portion	295,313
Less: unamortized discount and issuance costs	(23,382)
Less: current portion of long-term debt	(6,250)	$ (6,250)
Total long-term debt	265,681	$ 266,872
Senior Facilities
Debt Instrument [Line Items]
2021	3,125
2022	6,250
2023	10,938
2024	12,500
2025	87,500
Total before unamortized discount and issuance costs and current portion	120,313
Less: unamortized discount and issuance costs	(2,339)
Less: current portion of long-term debt	(6,250)
Total long-term debt	111,724
Convertible Senior Notes
Debt Instrument [Line Items]
2025	175,000
Total before unamortized discount and issuance costs and current portion	175,000
Less: unamortized discount and issuance costs	(21,043)
Total long-term debt	$ 153,957

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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