NET ASSETS - Summary of Common Stock Dividends Declared (Details) - $ / shares	Jun. 30, 2023	Mar. 31, 2023	Dec. 30, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020
Quarterly common dividend declared
Dividends Payable [Line Items]
Common dividend declared (in dollars per share)	$ 0.37	$ 0.37	$ 0.36	$ 0.34	$ 0.32	$ 0.32	$ 0.32	$ 0.32	$ 0.32	$ 0.32	$ 0.32
Supplemental common dividend declared
Dividends Payable [Line Items]
Common dividend declared (in dollars per share)	$ 0.07	$ 0.07	$ 0.08	$ 0.06	$ 0.08	$ 0.08	$ 0.07	$ 0.06	$ 0.04	$ 0.05