Debt and Foreign Currency Transactions and Translations -- Additional Information (Details)					3 Months Ended		12 Months Ended
	Dec. 13, 2023 USD ($)	Apr. 19, 2023	Jul. 16, 2021 USD ($)	Mar. 03, 2015 USD ($)	Mar. 31, 2024 USD ($) Installment		Dec. 31, 2023 USD ($)		Dec. 23, 2024 USD ($)	Dec. 22, 2024 USD ($)	Nov. 02, 2023 USD ($)	Nov. 19, 2022 USD ($)	Apr. 04, 2019	Apr. 04, 2018
Debt Instrument [Line Items]
Aggregate principal amount					$ 2,492,000,000		$ 2,492,000,000
MFIC Bethesda CLO 1 LLC Debt Securitization
Debt Instrument [Line Items]
Term debt securitization											$ 402,360,000
Senior Secured Facility
Debt Instrument [Line Items]
Required assets coverage percentage													150.00%	200.00%
Final Maturity Date					Apr. 19, 2028		Apr. 19, 2028
Aggregate principal amount					$ 1,705,000,000	[1]	$ 1,705,000,000	[2]
Date of first required payment to repay					Apr. 19, 2027
Number of installment | Installment					12
Frequency of payment and payment terms					Commencing April 19, 2027, the Company is required to repay, in twelve consecutive monthly installments of equal size, the outstanding amount under the Senior Secured Facility as of April 19, 2027.
Frequency of periodic payment					monthly
Commitment fee per annum					0.375%
Required minimum percentage of equity to assets					30.00%
Base amount considered for covenants					$ 705,000,000
Considered percentage of net proceeds from sale of equity interest for covenants					25.00%
Credit facility expiration date		Apr. 19, 2028
Maximum borrowing capacity					$ 1,705,000,000		1,705,000,000					$ 1,810,000,000
Maximum borrowing capacity under accordian feature					2,325,000,000
Available remaining capacity					$ 1,062,599,000		$ 1,004,732,000
Senior Secured Facility | Forecast
Debt Instrument [Line Items]
Maximum borrowing capacity									$ 1,550,000,000	$ 1,705,000,000
2025 Notes
Debt Instrument [Line Items]
Final Maturity Date				Mar. 03, 2025	Mar. 03, 2025		Mar. 03, 2025
Aggregate principal amount				$ 350,000,000	$ 350,000,000		$ 350,000,000
Date of first required payment to repay				Sep. 03, 2015
Frequency of payment and payment terms					The 2025 Notes will mature on March 3, 2025. Interest on the 2025 Notes is due semi-annually on March 3 and September 3, at an annual rate of 5.25%, commencing on September 3, 2015.
Frequency of periodic payment				semi-annually
Net proceeds from senior unsecured notes				$ 343,650,000
Annual interest rate				5.25%
2026 Notes
Debt Instrument [Line Items]
Final Maturity Date			Jul. 16, 2026		Jul. 16, 2026		Jul. 16, 2026
Aggregate principal amount			$ 125,000,000		$ 125,000,000		$ 125,000,000
Date of first required payment to repay			Jan. 16, 2022
Frequency of payment and payment terms					The 2026 Notes will mature on July 16, 2026. Interest on the 2026 Notes is due semi-annually on January 16 and July 16, at an annual rate of 4.50%, commencing on January 16, 2022.
Frequency of periodic payment			semi-annually
Net proceeds from senior unsecured notes			$ 122,965,000
Annual interest rate			4.50%
2028 Notes
Debt Instrument [Line Items]
Final Maturity Date	Dec. 15, 2028				Dec. 15, 2028		Dec. 15, 2028
Aggregate principal amount	$ 80,000,000				$ 80,000,000		$ 80,000,000
Redemption period, start date	Dec. 15, 2025
Debt instrument redemption rate per note	$ 25,000
Frequency of payment and payment terms					The 2028 Notes will mature on December 15, 2028. The 2028 Notes bear interest at a rate of 8.00% per year, commencing December 13, 2023.
Annual interest rate	8.00%
2028 Notes | Over-allotment Option
Debt Instrument [Line Items]
Aggregate principal amount	$ 5,000,000
Maximum | Senior Secured Facility
Debt Instrument [Line Items]
Fronting fees on letters of credit issued					2.25%
Maximum | Senior Secured Facility | SOFR
Debt Instrument [Line Items]
Borrowing base interest rate					1.975%
Maximum | Senior Secured Facility | Alternate Base Rate
Debt Instrument [Line Items]
Borrowing base interest rate					0.875%
Minimum | Senior Secured Facility
Debt Instrument [Line Items]
Required indebtedness ratio for covenants					1.5
Minimum | Senior Secured Facility | SOFR
Debt Instrument [Line Items]
Borrowing base interest rate					1.85%
Minimum | Senior Secured Facility | Alternate Base Rate
Debt Instrument [Line Items]
Borrowing base interest rate					0.75%
Standby Letters of Credit | Senior Secured Facility
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 150,000,000
Line of credit					$ 17,291,000		$ 17,291,000

[1] Prior to November 19, 2022, total lender commitments were $1,810,000. As of March 31, 2024, total lender commitments were $1,705,000. The total lender commitments will remain $1,705,000 until December 22, 2024 and will decrease to $1,550,000 thereafter.

[2] Prior to November 19, 2022, total lender commitments were $1,810,000. As of December 31, 2023, total lender commitments were $1,705,000.