Borrowings - Narrative (Details)	Feb. 06, 2019	Feb. 05, 2019	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Debt Disclosure [Abstract]
Asset coverage ratio	150.00%	200.00%	181.70%	200.04%	232.15%	220.31%	269.51%
Total consolidated asset ratio	200.00%	100.00%