CONSOLIDATED STATEMENTS OF CHANGES IN NET ASSETS - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Investment Company, Net Assets [Roll Forward]
Beginning balance (in shares)		36,076,425		24,959,000	36,076,425	24,959,000	21,005,000
Beginning balance		$ 590,408		$ 420,867	$ 590,408	$ 420,867	$ 336,251
Beginning balance (in shares)		2,339,512			2,339,512
Issuance of common stock					$ 181,387	202,781	98,107
Cancellation of treasury shares					0
Share-based compensation					4,518	3,705	3,585
Issuance of common stock under restricted stock plan, net of forfeitures					0	0	0
Common stock withheld for payroll taxes upon vesting of restricted stock					(1,063)	(1,021)	(1,408)
Dividends to shareholders					(102,925)	(71,102)	(58,624)
Change in restoration plan liability					(38)	2,085	141
Reclassification for certain permanent book-to-tax differences					0	0	0
Net investment income	$ 29,396	$ 24,556	$ 22,404	12,438	110,005	68,711	42,687
Net realized loss on investments, extinguishment of debt and disposal of fixed assets					(40,256)	(17,029)	(11,339)
Net unrealized (appreciation) depreciation on investments	$ 3,734	$ 12,038	$ (4,600)	$ (12,248)	$ 13,640	$ (18,589)	$ 11,467
Ending balance (in shares)	45,050,759		36,076,425		45,050,759	36,076,425	24,959,000
Ending balance	$ 755,676		$ 590,408		$ 755,676	$ 590,408	$ 420,867
Ending balance (in shares)	0		2,339,512		0	2,339,512
Common Stock
Investment Company, Net Assets [Roll Forward]
Beginning balance (in shares)		36,076,425		24,958,520	36,076,425	24,958,520	21,005,324
Beginning balance		$ 9,604		$ 6,825	$ 9,604	$ 6,825	$ 5,836
Issuance of common stock (in shares)					8,733,315	10,969,898	3,872,031
Issuance of common stock					$ 2,183	$ 2,742	$ 969
Cancellation of treasury shares					$ (585)
Issuance of common stock under restricted stock plan, net of forfeitures (in shares)					293,816	197,597	133,289
Issuance of common stock under restricted stock plan, net of forfeitures					$ 74	$ 49	$ 33
Common stock withheld for payroll taxes upon vesting of restricted stock (in shares)					(52,797)	(49,590)	(52,124)
Common stock withheld for payroll taxes upon vesting of restricted stock					$ (13)	$ (12)	$ (13)
Ending balance (in shares)	45,050,759		36,076,425		45,050,759	36,076,425	24,958,520
Ending balance	$ 11,263		$ 9,604		$ 11,263	$ 9,604	$ 6,825
Treasury Stock
Investment Company, Net Assets [Roll Forward]
Beginning balance		$ (23,937)		$ (23,937)	$ (23,937)	$ (23,937)	$ (23,937)
Beginning balance (in shares)		2,339,512		2,339,512	2,339,512	2,339,512	2,339,512
Cancellation of treasury shares (in shares)					(2,339,512)
Cancellation of treasury shares					$ 23,937
Ending balance	$ 0		$ (23,937)		$ 0	$ (23,937)	$ (23,937)
Ending balance (in shares)	0		2,339,512		0	2,339,512	2,339,512
Additional Paid-In Capital
Investment Company, Net Assets [Roll Forward]
Beginning balance		$ 646,586		$ 448,235	$ 646,586	$ 448,235	$ 356,447
Issuance of common stock					179,204	200,039	97,138
Cancellation of treasury shares					(23,352)
Share-based compensation					4,518	3,705	3,585
Issuance of common stock under restricted stock plan, net of forfeitures					(74)	(49)	(33)
Common stock withheld for payroll taxes upon vesting of restricted stock					(1,050)	(1,009)	(1,395)
Change in restoration plan liability					(38)	2,085	141
Reclassification for certain permanent book-to-tax differences					(8,849)	(6,420)	(7,648)
Ending balance	$ 796,945		$ 646,586		796,945	646,586	448,235
Total Distributable Earnings (Loss)
Investment Company, Net Assets [Roll Forward]
Beginning balance		$ (41,845)		$ (10,256)	(41,845)	(10,256)	(2,095)
Dividends to shareholders					(102,925)	(71,102)	(58,624)
Reclassification for certain permanent book-to-tax differences					8,849	6,420	7,648
Net investment income					110,005	68,711	42,687
Net realized loss on investments, extinguishment of debt and disposal of fixed assets					(40,256)	(17,029)	(11,339)
Net unrealized (appreciation) depreciation on investments					13,640	(18,589)	11,467
Ending balance	$ (52,532)		$ (41,845)		$ (52,532)	$ (41,845)	$ (10,256)