INCOME AND EXCISE TAXES - Summary of Dividends Paid Per Common Share (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Ordinary income (in dollars per share)	$ 1.80	$ 1.62	$ 1.60
Capital gains (in dollars per share)	0.07	0	0
Total (in dollars per share)	1.87	1.62	1.60	$ 1.68	$ 1.54	$ 1.52	$ 1.52	$ 1.57	$ 1.57	$ 1.57
Dividend income per share (in dollars per share)	$ 0.0582	$ 0.0461	$ 0.0157
Dividend Concentration Risk | Dividends | Interest-Related Dividends
Investments, Owned, Federal Income Tax Note [Line Items]
Composition, percent of fair value	76.60%	84.60%	88.40%