Fair Value Measurements - Fair Value Levels (Details) - USD ($) $ in Thousands	Mar. 31, 2023		Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 2,136,533	[1],[2]	$ 1,975,109	[3],[4]
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	452,478		460,379
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,684,055		1,514,730
First Lien Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,082,113		1,919,673
First Lien Debt | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0		0
First Lien Debt | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	452,478		460,379
First Lien Debt | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,629,635		1,459,294
Second Lien Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	24,061		26,043
Second Lien Debt | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0		0
Second Lien Debt | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0		0
Second Lien Debt | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	24,061		26,043
Other Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	30,359		29,393
Other Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0		0
Other Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0		0
Other Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 30,359		$ 29,393

[1] Unless otherwise indicated, issuers of debt and equity investments held by the Company (which such term “Company” shall include the Company’s consolidated subsidiaries for purposes of this Consolidated Schedule of Investments) are denominated in dollars. All debt investments are income producing unless otherwise indicated. All equity investments are non-income producing unless otherwise noted. Certain portfolio company investments are subject to contractual restrictions on sales. Under the Investment Company Act of 1940, as amended (together with the rules and regulations promulgated thereunder, the “1940 Act”), the Company would be deemed to “control” a portfolio company if the Company owned more than 25% of its outstanding voting securities and/or held the power to exercise control over the management or policies of the portfolio company. As of March 31, 2023, the Company does not “control” any of these portfolio companies. Under the 1940 Act, the Company would be deemed an “affiliated person” of a portfolio company if the Company owns 5% or more of the portfolio company’s outstanding voting securities. As of March 31, 2023, the Company is not an “affiliated person” of any of its portfolio companies.

[2] Unless otherwise indicated, the Company's investments are pledged as collateral supporting the amounts outstanding under the ING Facility (as defined below). See Note 6 "Debt".

[3] Unless otherwise indicated, issuers of debt and equity investments held by the Company are denominated in dollars. All debt investments are income producing unless otherwise indicated. All equity investments are non-income producing unless otherwise noted. Certain portfolio company investments are subject to contractual restrictions on sales. Under the 1940 Act, the Company would be deemed to “control” a portfolio company if the Company owned more than 25% of its outstanding voting securities and/or held the power to exercise control over the management or policies of the portfolio company. As of December 31, 2022, the Company does not “control” any of these portfolio companies. Under the 1940 Act, the Company would be deemed an “affiliated person” of a portfolio company if the Company owns 5% or more of the portfolio company’s outstanding voting securities. As of December 31, 2022, the Company is not an “affiliated person” of any of its portfolio companies.

[4] Unless otherwise indicated, the Company's investments are pledged as collateral supporting the amounts outstanding under the ING Facility (as defined below). See Note 6 "Debt".