Revolving Credit Facility - Components of Interest Expense (Details) - Line of Credit - Revolving Credit Facility - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Line of Credit Facility [Line Items]
Interest expense	$ 956	$ 1,084	$ 2,958	$ 3,403
Amortization of deferred financing costs	168	166	484	484
Unused commitment fees	47	52	129	199
Total interest expense	$ 1,171	$ 1,302	$ 3,571	$ 4,086