INCOME TAXES - Net Assets Resulting From Operations To Estimated RIC Taxable Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Net increase in net assets from operations	$ 18,176	$ 2,949	$ 9,458	$ 2,510	$ 19,669	$ 12,560	$ (4,556)	$ 15,142	$ 33,093	$ 42,815	$ 50,883
Net unrealized depreciation (appreciation) on investments									18,589	(11,467)	(28,755)
Income/gain (expense/loss) recognized for tax on pass-through entities									962	3,753	(11,000)
(Gain) loss recognized on dispositions									(1,473)	152	2,206
Capital loss carryover									12,796	(878)	17,924
Net operating income - wholly-owned subsidiary									809	(10,757)	(378)
Dividend income from wholly-owned subsidiary									1,068	4,000	0
Non-deductible tax expense									628	65	1,066
Loss on extinguishment of debt									(2,726)	12,268	0
Non-deductible compensation									3,243	3,679	0
Compensation related book/tax differences									812	36	0
Interest on non-accrual loans									3,343	4,171	0
Other book/tax differences									1,191	1,530	870
Estimated distributable income before deductions for distributions									72,335	49,367	32,816
Ordinary									70,034	57,518	38,917
Capital gains									0	0	0
Deemed distributions									0	0	0
Distributions payable									0	0	0
Estimated annual RIC undistributed taxable income									2,301	$ (8,151)	$ (6,101)
Capital loss carryover	$ 30,200								$ 30,200