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Fair Value Measurements - Summary of Changes in Fair Value of Investments Measured Using Level 3 Inputs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Total Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 9,472,796	$ 9,501,329
Purchases of investments	1,508,759	952,854
Proceeds from principal repayments and sales of investments	(1,187,790)	(1,042,362)
Accretion of discount/amortization of premium	50,580	45,270
Transfers into Level 3	4,938	108,674
Transfers out of Level 3	(91,939)	0
Fair value, end of period	9,710,582	9,472,796
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the Consolidated Statements of Operations	(44,082)	(97,281)
Investments, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(1,662)	39,361
Investments, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(45,100)	(132,330)
First lien debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	9,275,511	9,288,184
Purchases of investments	1,492,985	934,505
Proceeds from principal repayments and sales of investments	(1,114,974)	(980,395)
Accretion of discount/amortization of premium	50,516	45,133
Transfers into Level 3	4,938	108,674
Transfers out of Level 3	(91,939)	0
Fair value, end of period	9,564,203	9,275,511
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the Consolidated Statements of Operations	(38,013)	(119,180)
Debt Securities, First Lien, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(15,095)	(2,125)
Debt Securities, First Lien, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(37,739)	(118,465)
Second lien debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	46,336	42,880
Purchases of investments	1,935	5,949
Proceeds from principal repayments and sales of investments	(7,351)	0
Accretion of discount/amortization of premium	58	137
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, end of period	41,515	46,336
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the Consolidated Statements of Operations	374	(2,629)
Debt Securities, Second Lien, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(49)	0
Debt Securities, Second Lien, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	586	(2,630)
Unsecured debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	0
Purchases of investments	9,924
Proceeds from principal repayments and sales of investments	0
Accretion of discount/amortization of premium	6
Transfers into Level 3	0
Transfers out of Level 3	0
Fair value, end of period	9,924	0
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the Consolidated Statements of Operations	(6)
Unsecured Debt, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	0
Unsecured Debt, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(6)
Investments in equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	150,949	170,265
Purchases of investments	3,915	12,400
Proceeds from principal repayments and sales of investments	(65,465)	(61,967)
Accretion of discount/amortization of premium	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair value, end of period	94,940	150,949
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the Consolidated Statements of Operations	(6,437)	24,528
Equity Securities, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	13,482	41,486
Equity Securities, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	$ (7,941)	$ (11,235)

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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Accretion Of Discount/Amortization Of Premium

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Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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