Fair Value Measurements - Summary of Changes in Fair Value of Investments Measured Using Level 3 Inputs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Total
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 13,595,554	$ 11,871,994	$ 13,595,554	$ 11,871,994	$ 13,036,526	$ 12,976,765	$ 11,127,846	$ 9,710,582
Purchases of investments	1,033,870	980,418	2,300,878	2,631,739
Proceeds from principal repayments and sales of investments	(435,950)	(296,497)	(1,598,191)	(569,172)
Accretion of discount (amortization of premium)	13,018	9,371	39,619	27,998
Transfers into level 3	8,360	57,016	8,585	50,239
Transfers out of level 3	0	0	(102,175)	(802)
Fair value, end of period	13,595,554	11,871,994	13,595,554	11,871,994
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the condensed consolidated statements of operations	(56,012)	(4,723)	(27,067)	20,426
Investments, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(9,270)	(17,283)	(1,977)	(16,660)
Investments, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(51,000)	11,123	(27,950)	38,070
First lien debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	13,257,332	11,712,831	13,257,332	11,712,831	12,800,357	12,714,636	10,975,967	9,564,203
Purchases of investments	928,219	974,120	2,190,326	2,620,371
Proceeds from principal repayments and sales of investments	(434,248)	(296,497)	(1,562,430)	(569,172)
Accretion of discount (amortization of premium)	12,913	9,336	39,343	27,895
Transfers into level 3	8,360	57,016	8,585	50,239
Transfers out of level 3	0	0	(102,175)	(802)
Fair value, end of period	13,257,332	11,712,831	13,257,332	11,712,831
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the condensed consolidated statements of operations	(54,660)	(5,674)	(25,068)	19,118
Debt Securities, First Lien, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(9,270)	(17,283)	(9,292)	(16,660)
Debt Securities, First Lien, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(48,999)	10,172	(21,661)	36,757
Second lien debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	226,249	42,415	226,249	42,415	122,942	119,184	41,985	41,515
Purchases of investments	104,168	534	107,954	1,215
Proceeds from principal repayments and sales of investments	(196)	0	(3,206)	0
Accretion of discount (amortization of premium)	94	24	244	72
Transfers into level 3	0	0	0	0
Transfers out of level 3	0	0	0	0
Fair value, end of period	226,249	42,415	226,249	42,415
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the condensed consolidated statements of operations	(759)	(128)	1,588	(387)
Debt Securities, Second Lien, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	0	0	(1)	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)	(759)	(128)	2,074	(387)
Unsecured debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	13,991	12,724	13,991	12,724	13,721	33,521	12,278	9,924
Purchases of investments	487	431	1,426	2,629
Proceeds from principal repayments and sales of investments	0	0	(20,595)	0
Accretion of discount (amortization of premium)	11	11	32	31
Transfers into level 3	0	0	0	0
Transfers out of level 3	0	0	0	0
Fair value, end of period	13,991	12,724	13,991	12,724
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the condensed consolidated statements of operations	(228)	4	(663)	134
Unsecured Debt, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	0	0	0	0
Unsecured Debt, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(228)	4	(393)	140
Investments in equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	97,982	104,024	97,982	104,024	$ 99,506	$ 109,424	$ 97,616	$ 94,940
Purchases of investments	996	5,333	1,172	7,524
Proceeds from principal repayments and sales of investments	(1,506)	0	(11,960)	0
Accretion of discount (amortization of premium)	0	0	0	0
Transfers into level 3	0	0	0	0
Transfers out of level 3	0	0	0	0
Fair value, end of period	97,982	104,024	97,982	104,024
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the condensed consolidated statements of operations	(365)	1,075	(2,924)	1,561
Equity Securities, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	0	0	7,316	0
Equity Securities, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	$ (1,014)	$ 1,075	$ (7,970)	$ 1,560