Long-Term Debt - Schedule of Interest Expense Related to Notes (Details) - 3.00% Convertible Senior Notes Due 2025 - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2021	Mar. 31, 2021
Debt Instrument [Line Items]
Contractual interest expense	$ 1,294	$ 2,616
Amortization of debt discount	863	1,731
Amortization of issuance costs	217	435
Total interest expense related to the Notes	$ 2,374	$ 4,782

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of amortization expense attributable to debt issuance costs.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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