Long-Term Debt, Net - Summary of Long-term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Debt issuance costs, net	$ (5,677)	$ (1,846)
Total long-term debt, net of issuance costs	123,227	139,298
Line of Credit | Revolving lines of credit to banks under the Senior Secured Credit Facility
Debt Instrument [Line Items]
Long-term debt	19,000	141,144
Exchangeable Notes | 1% Exchangeable Senior Notes due 2025
Debt Instrument [Line Items]
Long-term debt	109,904	$ 0
Debt issuance costs, net	$ (4,113)