Debt - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Sep. 11, 2024	Mar. 11, 2024	Nov. 24, 2020	Feb. 10, 2020
Line Of Credit Facility [Line Items]
Debt, Current borrowing capacity		$ 2,955,000		$ 2,555,000
Deferred financing costs		14,134		14,937
2025 Notes
Line Of Credit Facility [Line Items]
Aggregate principal amount		$ 360,000		360,000				$ 360,000
Interest rate								3.75%
Debt Instrument, Maturity Date, Description		The 2025 Notes bear interest at a rate of 3.75% per year, payable semi-annually. The 2025 Notes will mature on February 10, 2025 and may be redeemed in whole or in part at the Company’s option at any time or from time to time at the redemption prices set forth in the indenture.
2026 Notes
Line Of Credit Facility [Line Items]
Aggregate principal amount		$ 500,000		500,000			$ 500,000
Interest rate							2.875%
Debt Instrument, Maturity Date, Description		The 2026 Notes bear interest at a rate of 2.875% per year, payable semi-annually. The 2026 Notes will mature on January 15, 2026 and may be redeemed in whole or in part at the Company’s option at any time or from time to time at the redemption prices set forth in the indenture.
2027 Notes
Line Of Credit Facility [Line Items]
Aggregate principal amount		$ 400,000				$ 400,000
Interest rate						6.375%
Debt Instrument, Maturity Date, Description		The 2027 Notes bear interest at a rate of 6.375% per year, payable semi-annually, commencing on September 11, 2024. The 2027 Notes will mature on March 11, 2027 and may be redeemed in whole or in part at the Company’s option at any time or from time to time at the redemption prices set forth in the indenture.
Revolving Credit Facility
Line Of Credit Facility [Line Items]
Weighted average interest rates		7.36%	6.45%
Average outstanding balance		$ 912,596	$ 1,147,001
Debt, Current borrowing capacity	[1]	1,695,000		1,695,000
Maximum borrowing capacity		$ 2,542,500
Revolving credit facility interest rate description		Borrowings denominated in USD, including amounts drawn in respect of letters of credit, bear interest (at the Company’s election) of either (i) Term SOFR plus a margin of either (x) 2.00%, (y) 1.875% (subject to maintenance of certain long-term corporate debt ratings) or (z) 1.75% (subject to certain gross borrowing base conditions), in each case, plus an additional 0.10% credit adjustment spread or (ii) an alternative base rate, which is the highest of (a) zero, (b) the highest of (i) the Prime Rate in effect on such day, (ii) the Federal Funds Effective Rate for such day plus 1/2 of 1.00% and (iii) the rate per annum equal to (x) the greater of (A) Term SOFR for an interest period of one (1) month and (B) zero plus (y) 1.00%, plus a margin of either (x) 1.00%, (y) 0.875% (subject to maintenance of certain long-term corporate debt ratings) or (z) 0.75% (subject to certain gross borrowing base conditions). Borrowings denominated in non-USD bear interest of the applicable term benchmark rate or daily simple SONIA plus a margin of either 2.00%, 1.875% or 1.75% (subject to the conditions applicable to borrowings denominated in USD that bear interest based on the applicable term benchmark rate or daily simple SONIA) plus, in the case of borrowings denominated in Pound Sterling (GBP) only, an additional 0.1193% credit adjustment spread. With respect to borrowings denominated in USD, the Company may elect either Term SOFR, or an alternative base rate at the time of borrowing, and such borrowings may be converted from one benchmark to another at any time, subject to certain conditions. Interest is payable in arrears on the applicable interest payment date as specified therein. The Company pays a fee of 0.375% per annum on committed but undrawn amounts under the Revolving Credit Facility, payable quarterly in arrears. Any amounts borrowed under the Revolving Credit Facility with respect to certain lenders, which hold approximately 87% of total lending commitments, will mature, and all accrued and unpaid interest will be due and payable, on October 18, 2028. Any amounts borrowed under the Revolving Credit Facility with respect to remaining lenders, will mature, and all accrued and unpaid interest will be due and payable, on May 5, 2027.
Line of credit facility, commitment fee percentage		0.375%
Debt covenants minimum stockholders equity		$ 800,000
Net proceeds of the sale of equity interests		25.00%
Cost incurred in obtaining revolving credit facility		$ 33,254
Unamortized deferred financing costs		$ 14,134		$ 14,937
Revolving Credit Facility | Borrowings denominated in USD
Line Of Credit Facility [Line Items]
Additional credit adjustment spread		0.10%
Revolving Credit Facility | Borrowings denominated in Pound Sterling (GBP)
Line Of Credit Facility [Line Items]
Additional credit adjustment spread		0.1193%
Revolving Credit Facility | Minimum
Line Of Credit Facility [Line Items]
Asset coverage ratio		150.00%
Asset coverage ratio with respect to consolidated assets		200.00%
Revolving Credit Facility | Lenders Hold 87% of Total Lending Commitments
Line Of Credit Facility [Line Items]
Revolving credit facility accrued and unpaid interest due and payable date		Oct. 18, 2028
Revolving Credit Facility | Other Lenders
Line Of Credit Facility [Line Items]
Revolving credit facility accrued and unpaid interest due and payable date		May 05, 2027
Forecast
Line Of Credit Facility [Line Items]
Interest rate					6.375%
Debt
Line Of Credit Facility [Line Items]
Asset coverage ratio requirement, description		Investment Company Act, is at least 150% after such borrowing (if certain requirements are met). As of March 31, 2024 and December 31, 2023, the Company’s asset coverage ratio based on the aggregate amount outstanding of senior securities was 188% and 187%.
Asset coverage ratio		188.00%		187.00%
Weighted average interest rates		5.41%		5.31%
Average outstanding balance		$ 1,864,904		$ 1,930,027
Maximum borrowing capacity		$ 2,542,500

[1] Provides, under certain circumstances, a total borrowing capacity of $2,542,500. The Company may borrow amounts in USD or certain other permitted currencies. Debt outstanding denominated in currencies other than USD has been converted to USD using the applicable foreign currency exchange rate as of the applicable reporting date. As of March 31, 2024, the Company had outstanding borrowings denominated in USD of $503,674, in Euros of EUR 37,700, in GBP of GBP 26,000 and in CAD of CAD 9,020. As of December 31, 2023, the Company had outstanding borrowings denominated in USD of $890,674, in Euros of EUR 37,700, in GBP of GBP 26,000 and in CAD of CAD 9,020.