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, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Total Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 11,871,994	$ 9,318,628	$ 11,871,994	$ 9,318,628	$ 11,127,846	$ 9,710,582	$ 9,085,022	$ 9,472,796
Purchases of investments	980,418	401,065	2,631,739	645,232
Proceeds from principal repayments and sales of investments	(296,497)	(176,756)	(569,172)	(712,694)
Accretion of discount/(amortization of premium)	9,371	8,464	27,998	37,501
Transfers into level 3	57,016	0	50,239	4,938
Transfers out of level 3	0	0	(802)	(91,939)
Fair value, end of period	11,871,994	9,318,628	11,871,994	9,318,628
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	(4,723)	2,038	20,426	(30,655)
Investments, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(17,283)	(7,225)	(16,660)	(7,987)
Investments, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	11,123	8,058	38,070	(29,219)
First lien debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	11,712,831	9,166,292	11,712,831	9,166,292	10,975,967	9,564,203	8,934,769	9,275,511
Purchases of investments	974,120	399,838	2,620,371	643,168
Proceeds from principal repayments and sales of investments	(296,497)	(176,756)	(569,172)	(661,493)
Accretion of discount/(amortization of premium)	9,336	8,433	27,895	37,399
Transfers into level 3	57,016	0	50,239	4,938
Transfers out of level 3	0	0	(802)	(91,939)
Fair value, end of period	11,712,831	9,166,292	11,712,831	9,166,292
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	(5,674)	1,219	19,118	(27,360)
Debt Securities, First Lien, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(17,283)	(7,225)	(16,660)	(15,150)
Debt Securities, First Lien, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	10,172	7,233	36,757	(26,142)
Second lien debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	42,415	40,715	42,415	40,715	41,985	41,515	40,086	46,336
Purchases of investments	534	461	1,215	1,298
Proceeds from principal repayments and sales of investments	0	0	0	(7,351)
Accretion of discount/(amortization of premium)	24	31	72	102
Transfers into level 3	0	0	0	0
Transfers out of level 3	0	0	0	0
Fair value, end of period	42,415	40,715	42,415	40,715
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	(128)	137	(387)	168
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	0	(49)
Debt Securities, Second Lien, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	(128)	137	(387)	379
Unsecured debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	12,724		12,724		12,278	9,924
Purchases of investments	431		2,629
Proceeds from principal repayments and sales of investments	0		0
Accretion of discount/(amortization of premium)	11		31
Transfers into level 3	0		0
Transfers out of level 3	0		0
Fair value, end of period	12,724		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	4		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
Unsecured Debt, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	4		140
Investments in equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	104,024	111,621	104,024	111,621	$ 97,616	$ 94,940	$ 110,167	$ 150,949
Purchases of investments	5,333	766	7,524	766
Proceeds from principal repayments and sales of investments	0	0	0	(43,850)
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	104,024	111,621	104,024	111,621
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	1,075	682	1,561	(3,463)
Equity Securities, Realized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	0	0	0	7,212
Equity Securities, Unrealized Gain (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized gain (loss)	$ 1,075	$ 688	$ 1,560	$ (3,456)