CONSOLIDATED STATEMENTS OF CHANGES IN NET ASSETS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021
Investment Company, Net Assets [Roll Forward]
Net assets, beginning balance	$ 475,724	$ 452,985	$ 420,867	$ 381,945	$ 368,095	$ 336,251
Operations:
Net investment income	19,425	14,444	12,438	11,899	9,726	9,043
Total net realized (loss) gain on investments, net of tax	(11,086)	(8,635)	2,320	2,715	3,496	(952)
Net unrealized depreciation (appreciation) on investments	(5,390)	3,649	(12,248)	(2,054)	(691)	7,051
Realized loss on extinguishment of debt	0	0		0	(17,087)
Net increase (decrease) in net assets from operations	2,949	9,458	2,510	12,560	(4,556)	15,142
Dividends to shareholders	(19,275)	(14,287)	(16,615)	(22,917)	(12,401)	(11,528)
Capital share transactions:
Change in restoration plan liability	8	8	8	9	9	9
Issuance of common stock	101,469	26,500	46,035	15,754	29,880	27,686
Share-based compensation expense	992	1,060	821	849	923	1,076
Common stock withheld for payroll taxes upon vesting of restricted stock	(380)	0	(641)	(863)	(5)	(541)
Increase in net assets	85,763	22,739	32,118	5,392	13,850	31,844
Net assets, ending balance	$ 561,487	$ 475,724	$ 452,985	$ 387,337	$ 381,945	$ 368,095