Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Cash flows from operating activities
Net increase in net assets resulting from operations	$ 123,375	$ 105,480	$ 119,807
Adjustments to reconcile net increase (decrease) in net assets from operations to net cash used in operating activities:
Purchases of investments	(844,251)	(1,404,088)	(1,177,339)
Proceeds from principal payments and sales of investments	937,648	988,084	1,399,163
Net realized (gain) loss from investments	43,897	3,080	(21,226)
Net realized (gain) loss on foreign currency transactions	5,134	(5,292)	3,496
Net realized loss on extinguishment of debt		747	4,859
Net change in unrealized appreciation on forward currency exchange contracts	2,322	5,259	(27,935)
Net change in unrealized appreciation on investments	(29,470)	10,682	(15,972)
Net change in unrealized appreciation on foreign currency translation	(4,050)	3,644	936
Increase in investments due to PIK	(22,844)	(15,037)	(10,763)
Accretion of discounts and amortization of premiums	(5,329)	(4,934)	(5,674)
Amortization of deferred financing costs and debt issuance costs	3,570	3,896	5,731
Changes in operating assets and liabilities:
Collateral on forward currency exchange contracts	1,999	(6,797)	2,119
Interest receivable on investments	(2,899)	(15,001)	(3,549)
Prepaid Insurance	(16)	(1)	(193)
Dividend receivable	4,264	4,716	(10,808)
Interest payable	1,153	5,072	(1,165)
Base management fee payable	23	114	2,503
Incentive fee payable	(1,889)	4,489	928
Accounts payable and accrued expenses	6,627	(943)	636
Net cash provided by (used in ) in operating activities	219,264	(316,830)	265,554
Cash flows from financing activities
Borrowings on debt	348,000	792,747	1,425,050
Repayments on debt	(480,000)	(462,247)	(1,461,826)
Payments of financing costs		(4,366)
Payments of debt issuance costs			(14,053)
Stockholder distributions paid	(99,426)	(87,804)	(87,805)
Net cash provided by (used in) financing activities	(231,426)	238,330	(138,634)
Net increase (decrease) in cash, foreign cash, restricted cash and cash equivalents	(12,162)	(78,500)	126,920
Effect of foreign currency exchange rates	(1,084)	649	(5,041)
Cash, foreign cash, restricted cash and cash equivalents, beginning of year	125,730	203,581	81,702
Cash, foreign cash, restricted cash and cash equivalents, end of year	112,484	125,730	203,581
Supplemental disclosure of cash flow information:
Cash interest paid during the period	75,285	43,350	46,780
Cash paid for income taxes, including excise taxes during the period	1,216	134	237
Supplemental disclosure of non-cash information:
Debt investment sold by the Company to ISLP			317,077
Company investment into ISLP in exchange for investments sold			128,970
Company investment into Bain Capital Senior Loan Program, LLC		5,584
Deconsolidation of BCC Middle Market CLO 2018-1 LLC
Disposition of assets		470,616
Reduction of liabilities		(390,448)
Cash	42,995	30,205	87,443
Restricted cash	63,084	65,950	86,159
Foreign cash	6,405	29,575	29,979
Total cash, foreign cash, restricted cash, and cash equivalents shown in the consolidated statements of cash flows	$ 112,484	$ 125,730	$ 203,581