Long-Term Debt - Schedule of Interest Expense Related to Notes (Details) - 3.00% Convertible Senior Notes Due 2025 - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Debt Instrument [Line Items]
Contractual interest expense	$ 1,308	$ 431	$ 3,924	$ 431
Amortization of debt discount	886	276	2,617	276
Amortization of issuance costs	223	70	658	70
Total interest expense related to the Notes	$ 2,417	$ 777	$ 7,199	$ 777

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

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