NET ASSETS - Summary of Changes in Net Assets (Details) - USD ($) $ in Thousands										3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 19, 2024	Apr. 19, 2024	Jan. 19, 2024	Oct. 20, 2023	Jul. 21, 2023	Apr. 20, 2023	Jan. 20, 2023	Oct. 17, 2022	Jul. 15, 2022	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Investment Company, Net Assets [Roll Forward]
Net assets at beginning of period (in shares)												9,666,829
Net assets at beginning of period										$ 246,567	$ 141,469	$ 203,719	$ 109,672	$ 109,672
Common shares of beneficial interest issued										0	23,292	$ 36,386	48,611
Dividend reinvestment (in shares)	122,068	108,842	95,386	85,776	81,429	68,670	68,233	44,690	17,171			326,296		304,108	61,861
Dividend reinvestment	$ 2,603	$ 2,294	$ 1,996	$ 1,740	$ 1,627	$ 1,352	$ 1,351	$ 889	$ 346	2,603	1,627	$ 6,893	4,330	$ 6,070	$ 1,235
Net investment income (loss)										7,238	4,790	20,549	13,054
Net realized gain (loss)										(655)	(2)	(640)	7
Net change in unrealized appreciation (depreciation)										(922)	3,723	(819)	5,601
Dividends declared										$ (9,368)	(3,738)	$ (20,625)	(10,114)
Net assets at end of period (in shares)										11,709,773		11,709,773		9,666,829
Net assets at end of period										$ 245,463	$ 171,161	$ 245,463	$ 171,161	$ 203,719	$ 109,672
Common Shares of Beneficial Interest
Investment Company, Net Assets [Roll Forward]
Net assets at beginning of period (in shares)										11,587,705	6,974,983	9,666,829	5,568,950	5,568,950
Net assets at beginning of period										$ 12	$ 7	$ 10	$ 6	$ 6
Common shares of beneficial interest issued (in shares)										0	1,120,349	1,716,648	2,389,479
Common shares of beneficial interest issued										$ 0	$ 1	$ 2	$ 2
Dividend reinvestment (in shares)										122,068	81,429	326,296	218,332
Net assets at end of period (in shares)										11,709,773	8,176,761	11,709,773	8,176,761	9,666,829	5,568,950
Net assets at end of period										$ 12	$ 8	$ 12	$ 8	$ 10	$ 6
Capital in Excess of Par Value
Investment Company, Net Assets [Roll Forward]
Net assets at beginning of period										235,355	138,894	194,681	110,873	110,873
Common shares of beneficial interest issued										0	23,291	36,384	48,609
Dividend reinvestment										2,603	1,627	6,893	4,330
Net assets at end of period										237,958	163,812	237,958	163,812	194,681	110,873
Accumulated Net Investment Income (Loss)
Investment Company, Net Assets [Roll Forward]
Net assets at beginning of period										6,803	2,843	4,749	955	955
Net investment income (loss)										7,238	4,790	20,549	13,054
Dividends declared										(9,368)	(3,738)	(20,625)	(10,114)
Net assets at end of period										4,673	3,895	4,673	3,895	4,749	955
Accumulated Net Realized Gain (Loss)
Investment Company, Net Assets [Roll Forward]
Net assets at beginning of period										360	9	345	0	0
Net realized gain (loss)										(655)	(2)	(640)	7
Net assets at end of period										(295)	7	(295)	7	345	0
Accumulated Net Unrealized Appreciation (Depreciation)
Investment Company, Net Assets [Roll Forward]
Net assets at beginning of period										4,037	(284)	3,934	(2,162)	(2,162)
Net change in unrealized appreciation (depreciation)										(922)	3,723	(819)	5,601
Net assets at end of period										$ 3,115	$ 3,439	$ 3,115	$ 3,439	$ 3,934	$ (2,162)

Carlyle Secured Lending III 10-Q