Revolving Credit Facility - Components of Interest Expense (Details) - Line of Credit - Revolving Credit Facility - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Line of Credit Facility [Line Items]
Interest expense	$ 962	$ 1,179	$ 2,002	$ 2,319
Amortization of deferred financing costs	160	165	316	318
Unused commitment fees	43	74	82	147
Total interest expense	$ 1,165	$ 1,418	$ 2,400	$ 2,784