Common Stock Issuances (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	May 15, 2020	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Class of Stock [Line Items]
Proceeds from issuance of common stock		$ 0	$ 0	$ 300,427
Common Stock
Class of Stock [Line Items]
Issuance of common stock, net of offering and underwriting costs (in shares)	33,451,902
Shares issued, price per share (in dollars per share)	$ 9.17
Proceeds from issuance of common stock	$ 300,427
Investments in and advances to affiliates, balance (in shares)	3,191,448