Summary of Significant Accounting Policies - Other Non-Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Debt issuance costs, net	$ 1,519	$ 1,867
Prepayments to outside operators	1,845	284
Right of use assets	409	700
Other deposits	55	98
Total other non-current assets, net	$ 3,828	$ 2,949