Investments - Schedule of Financial Information for OBDC SLF (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2023		Sep. 30, 2022	Sep. 30, 2023		Sep. 30, 2022	Jun. 30, 2023	Dec. 31, 2022		Jun. 30, 2022	Dec. 31, 2021
Assets
Investments at fair value	$ 12,896,158	[1],[2],[3],[4]		$ 12,896,158	[1],[2],[3],[4]			$ 13,010,345	[5],[6],[7]
Amortized Cost	12,822,871	[1],[2],[3],[4],[8],[9]		12,822,871	[1],[2],[3],[4],[8],[9]			13,046,132	[5],[6],[7],[10],[11]
Interest receivable	107,112			107,112				108,085
Receivable for investments sold	2,198			2,198				0
Prepaid expenses and other assets	3,988			3,988				3,627
Total Assets	13,461,820			13,461,820				13,584,853
Liabilities
Debt	7,062,399			7,062,399				7,281,744
Unamortized debt issuance costs	80,535			80,535				95,647
Distributions payable	128,612			128,612				129,517
Accrued expenses and other liabilities	176,398			176,398				202,793
Total Liabilities	7,461,811			7,461,811				7,702,450
Members' Equity
Members' Equity	6,000,009		$ 5,847,788	6,000,009		$ 5,847,788	$ 5,948,964	5,882,403		$ 5,704,446	$ 5,937,877
Total Liabilities and Net Assets	13,461,820			13,461,820				13,584,853
Investment Income
Total investment income from non-controlled, non-affiliated investments	399,022		314,053	1,170,867		851,498
Expenses
Interest expense	110,445		81,210	324,416		209,935
Professional fees	3,890		3,788	11,697		11,022
Total Operating Expenses	206,239		165,675	607,782		453,247
Net Investment Income (Loss) Before Taxes	192,783		148,378	563,085		398,251
Tax expense (benefit)	2,730		1,604	8,495		3,998
Net Investment Income (Loss) After Taxes	190,053		146,774	554,590		394,253
Net Realized and Change in Unrealized Gain (Loss) on Investments
Net change in unrealized gain (loss) on investments	16,989		118,587	102,531		(123,423)
Net realized gain on investments	(104)		66	(52,776)		3,635
Total Net Realized and Change in Unrealized Gain (Loss)	16,885		118,653	49,755		(119,788)
Net Increase (Decrease) in Net Assets Resulting from Operations	206,938		265,427	604,345		274,465
OBDC Senior Loan Fund
Assets
Investments at fair value	1,082,711			1,082,711				997,385
Amortized Cost	1,103,369			1,103,369				1,033,388
Cash	38,217			38,217				27,914
Interest receivable	7,505			7,505				3,920
Prepaid expenses and other assets	58,105			58,105				6,108
Total Assets	1,188,736			1,188,736				1,035,327
Liabilities
Debt	719,643			719,643				685,265
Unamortized debt issuance costs	5,240			5,240				6,117
Distributions payable	14,449			14,449				11,095
Payable for investments purchased	21,502			21,502				0
Accrued expenses and other liabilities	10,615			10,615				8,703
Total Liabilities	766,209			766,209				705,063
Members' Equity
Members' Equity	422,527			422,527				330,264
Total Liabilities and Net Assets	1,188,736			1,188,736				$ 1,035,327
Investment Income
Interest income	29,362		19,140	79,868		41,884
Other income	91		772	222		1,993
Total investment income from non-controlled, non-affiliated investments	29,453		19,912	80,090		43,877
Expenses
Interest expense	13,817		7,419	37,873		14,965
Professional fees	336		243	823		719
Total Operating Expenses	14,153		7,662	38,696		15,684
Net Investment Income (Loss) Before Taxes	15,300		12,250	41,394		28,193
Tax expense (benefit)	(920)		436	272		(184)
Net Investment Income (Loss) After Taxes	16,220		11,814	41,122		28,377
Net Realized and Change in Unrealized Gain (Loss) on Investments
Net change in unrealized gain (loss) on investments	4,767		599	15,345		(33,610)
Net realized gain on investments	(1,500)		0	(3,146)		20
Total Net Realized and Change in Unrealized Gain (Loss)	3,267		599	12,199		(33,590)
Net Increase (Decrease) in Net Assets Resulting from Operations	$ 19,487		$ 12,413	$ 53,321		$ (5,213)

[1] Certain portfolio company investments are subject to contractual restrictions on sales. Refer to footnote 28 for additional information on our restricted securities.

[2] Unless otherwise indicated, all investments are considered Level 3 investments.

[3] Unless otherwise indicated, loan contains a variable rate structure and may be subject to an interest rate floor. Variable rate loans bear interest at a rate that may be determined by reference to either the Secured Overnight Financing Rate ("SOFR" or "S," which can include one-, three- or six- month SOFR), London Interbank Offered Rate (“LIBOR” or “L”, which can include one-, three- or six- month LIBOR), Euro Interbank Offered Rate (“EURIBOR”), Great Britain Pound London Interbank Offered Rate (“GBPLIBOR” or “G”, which can include three- or six-month GBPLIBOR), SONIA ("SONIA” or "SA") or an alternate base rate (which can include the Federal Funds Effective Rate or the Prime Rate), at the borrower’s option, and which reset periodically based on the terms of the loan agreement.

[4] Unless otherwise indicated, the Company’s portfolio companies are pledged as collateral supporting the amounts outstanding under the Revolving Credit Facility, SPV Asset Facilities and CLOs. See Note 6 “Debt”.

[5] Certain portfolio company investments are subject to contractual restrictions on sales. Refer to footnote 28 for additional information on our restricted securities.

[6] Unless otherwise indicated, all investments are considered Level 3 investments.

[7] Unless otherwise indicated, the Company’s portfolio companies are pledged as collateral supporting the amounts outstanding under the Revolving Credit Facility, SPV Asset Facilities and CLOs. See Note 6 “Debt”.

[8] As of September 30, 2023, the net estimated unrealized loss for U.S. federal income tax purposes was $38.5 million based on a tax cost basis of $12.9 billion. As of September 30, 2023, the estimated aggregate gross unrealized loss for U.S. federal income tax purposes was $343.2 million and the estimated aggregate gross unrealized gain for U.S. federal income tax purposes was $304.7 million.

[9] The amortized cost represents the original cost adjusted for the amortization or accretion of premium or discount, as applicable, on debt investments using the effective interest method.

[10] As of December 31, 2022, the net estimated unrealized loss for U.S. federal income tax purposes was $126.2 million based on a tax cost basis of $13.1 billion. As of December 31, 2022, the estimated aggregate gross unrealized loss for U.S. federal income tax purposes was $382.2 million and the estimated aggregate gross unrealized gain for U.S. federal income tax purposes was $256.0 million.

[11] The amortized cost represents the original cost adjusted for the amortization or accretion of premium or discount , as applicable, on debt investments using the effective interest method.