Debt and Foreign Currency Transactions and Translations - Summarizes Average and Maximum Debt Outstanding and Interest and Debt Issuance Cost (Parenthetical) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Debt Instrument [Line Items]
Maximum amount of debt outstanding	[1]	$ 2,053,954	$ 1,511,548	$ 2,325,684	$ 1,511,548
Senior Secured Facility
Debt Instrument [Line Items]
Commitment fee for unused portion of facility		$ 532	$ 958	1,164	$ 1,997
MFIC Bethesda CLO II LLC Notes (Class A-1, Class A-2, Class B and Class C)
Debt Instrument [Line Items]
Maximum amount of debt outstanding				$ 399,000

[1] The maximum amount of debt outstanding during the six months ended June 30, 2025 is inclusive of $399 million of Class A1, Class A2, Class B, and Class C Notes of MFIC Bethesda CLO 2 that were sold on February 24, 2025. The Company used the proceeds received to repay borrowings under its Senior Secured Facility on February 25, 2025, the day following the closing of MFIC Bethesda CLO 2.