Fair Value Measurement - Summary of Changes in Fair Value of Level 3 Assets By Investment Type (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net Change in Unrealized Appreciation (Depreciation) for assets still held	$ (107,080)	$ (9,611)
1st Lien/Senior Secured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net Change in Unrealized Appreciation (Depreciation) for assets still held	(48,812)	7,799
1st Lien/Last-Out Unitranche
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net Change in Unrealized Appreciation (Depreciation) for assets still held	(3,754)	955
2nd Lien/Senior Secured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net Change in Unrealized Appreciation (Depreciation) for assets still held	(34,168)	(5,520)
Unsecured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net Change in Unrealized Appreciation (Depreciation) for assets still held	(288)	40
Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net Change in Unrealized Appreciation (Depreciation) for assets still held	(10,726)	(379)
Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net Change in Unrealized Appreciation (Depreciation) for assets still held	(7,950)	(11,558)
Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net Change in Unrealized Appreciation (Depreciation) for assets still held	(1,382)	(948)
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning Balance	3,270,660	3,050,769
Purchases	744,591	1,052,461
Net Realized Gain (Loss)	(7,125)	41,316
Net Change in Unrealized Appreciation (Depreciation)	(104,736)	(75,667)
Sales and Settlements	(504,874)	(1,136,897)
Net Amortization of Premium/Discount	28,565	62,227
Transfers In	50,220
Transfers Out		(95,946)
Ending Balance	3,477,301	2,898,263
Level 3 | 1st Lien/Senior Secured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning Balance	2,843,010	2,384,944
Purchases	693,066	988,448
Net Realized Gain (Loss)	(5,195)	(937)
Net Change in Unrealized Appreciation (Depreciation)	(43,422)	(11,352)
Sales and Settlements	(395,716)	(847,532)
Net Amortization of Premium/Discount	21,438	46,909
Transfers Out		(43,275)
Ending Balance	3,113,181	2,517,205
Level 3 | 1st Lien/Last-Out Unitranche
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning Balance	162,532	143,231
Purchases	18,982	31,138
Net Change in Unrealized Appreciation (Depreciation)	(5,773)	583
Sales and Settlements	(61,194)	(14,477)
Net Amortization of Premium/Discount	3,591	1,706
Ending Balance	118,138	162,181
Level 3 | 2nd Lien/Senior Secured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning Balance	178,780	407,872
Purchases	16,282	17,078
Net Realized Gain (Loss)	(2,035)	(1,203)
Net Change in Unrealized Appreciation (Depreciation)	(35,195)	(8,888)
Sales and Settlements	(47,859)	(209,051)
Net Amortization of Premium/Discount	3,502	13,610
Transfers In	50,220
Transfers Out		(52,671)
Ending Balance	163,695	166,747
Level 3 | Unsecured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning Balance	1,733	334
Purchases	6,182	1,433
Net Change in Unrealized Appreciation (Depreciation)	(288)	40
Net Amortization of Premium/Discount	34	2
Ending Balance	7,661	1,809
Level 3 | Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning Balance	52,655	48,080
Purchases		7,086
Net Realized Gain (Loss)		24,233
Net Change in Unrealized Appreciation (Depreciation)	(10,726)	(24,786)
Sales and Settlements		(34,438)
Ending Balance	41,929	20,175
Level 3 | Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning Balance	30,100	65,284
Purchases	10,079	7,278
Net Realized Gain (Loss)	105	19,223
Net Change in Unrealized Appreciation (Depreciation)	(7,950)	(30,316)
Sales and Settlements	(105)	(31,399)
Ending Balance	32,229	30,070
Level 3 | Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning Balance	1,850	1,024
Net Change in Unrealized Appreciation (Depreciation)	(1,382)	(948)
Ending Balance	$ 468	$ 76