Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Cash Flows from Operating Activities
Net Increase (Decrease) in Net Assets Resulting from Operations	$ 206,938	$ 265,427	$ 604,345	$ 274,465
Adjustments to reconcile net increase (decrease) in net assets resulting from operations to net cash used in operating activities:
Purchases of investments, net			(1,107,158)	(1,894,552)
Proceeds from investments and investment repayments, net			1,471,439	1,749,362
Net amortization/accretion of premium/discount on investments			(32,094)	(33,594)
Payment-in-kind interest and dividends			(161,080)	(101,236)
Net change in unrealized (gain) loss on investments			(106,470)	115,913
Net change in unrealized gain (loss) on interest rate swap attributed to unsecured notes			4,916	(88,985)
Net change in unrealized (gains) losses on translation of assets and liabilities in foreign currencies			(276)	7,735
Net realized (gain) loss on investments			52,129	(4,853)
Net realized (gain) loss on foreign currency transactions relating to investments			25	1,567
Amortization of debt issuance costs	6,152	6,311	20,577	21,133
Changes in operating assets and liabilities:
(Increase) decrease in interest receivable			973	(13,432)
(Increase) decrease in receivable from a controlled affiliate			(4,823)	(16,350)
(Increase) decrease in prepaid expenses and other assets			(361)	17,084
Increase (decrease) in management fee payable			213	116
Increase (decrease) in incentive fee payable			5,852	1,892
Increase (decrease) in payables to affiliate			(59)	(802)
Increase (decrease) in accrued expenses and other liabilities			(26,395)	87,059
Net cash provided by (used in) operating activities			721,753	122,522
Cash Flows from Financing Activities
Borrowings on debt			895,493	2,208,630
Payments on debt			(1,137,194)	(1,944,391)
Debt issuance costs			(5,465)	(14,179)
Repurchases of common stock			(34,058)	(10,015)
Cash distributions paid to shareholders			(453,586)	(354,522)
Net cash provided by (used in) financing activities			(734,810)	(114,477)
Net increase (decrease) in cash and restricted cash, including foreign cash (restricted cash of $(7,156) and $72,670, respectively)			(13,057)	8,045
Cash and restricted cash, including foreign cash, beginning of period (restricted cash of $96,420 and $21,481, respectively)			445,087	447,145	$ 447,145
Cash and restricted cash, including foreign cash, end of period (restricted cash of $89,264 and $94,151, respectively)	432,030	455,190	432,030	455,190	$ 445,087
Supplemental and Non-Cash Information
Interest paid during the period			312,242	177,362
Distributions declared during the period			452,681	366,490
Reinvestment of distributions during the period			0	11,951
Distributions Payable	$ 128,612	$ 122,085	128,612	122,085
Taxes, including excise tax, paid during the period			$ 1,705	$ 1,668