Debt - Schedule of Outstanding Debt Obligations (Details) - USD ($)	Sep. 30, 2024	Aug. 20, 2024	Aug. 15, 2024	Apr. 04, 2024	Feb. 29, 2024	Feb. 28, 2024	Dec. 31, 2023	Dec. 13, 2023	Feb. 22, 2023	Dec. 16, 2022	Dec. 15, 2022	Jul. 15, 2022
Debt Instrument [Line Items]
Total Debt	$ 4,403,000,000						$ 2,913,000,000
Outstanding Principal	2,515,909,000						2,051,355,000
Total Debt	1,475,228,000						632,976,000
Unamortized Debt Issuance Costs	46,521,000						26,047,000
Net Carrying Value	2,490,811,000						2,025,308,000
Unsecured debt investments
Debt Instrument [Line Items]
Aggregate Principal Committed				$ 700,000,000
Subscription Credit Facility | Line of credit
Debt Instrument [Line Items]
Aggregate Principal Committed	800,000,000						800,000,000			$ 800,000,000.0	$ 700,000,000.0
Outstanding Principal	535,000,000						800,000,000
Amount Available	265,000,000						0
Unamortized Debt Issuance Costs	843,000						2,546,000
Net Carrying Value	534,157,000						797,454,000
Revolving Credit Facility | Line of credit | Revolving Credit Facility
Debt Instrument [Line Items]
Aggregate Principal Committed	1,075,000,000				$ 950,000,000	$ 850,000,000	825,000,000
Aggregate Principal Committed					$ 75,000,000	$ 50,000,000
Outstanding Principal	365,409,000						288,355,000
Amount Available	709,591,000						536,645,000
Unamortized Debt Issuance Costs	8,703,000						9,275,000
Net Carrying Value	356,706,000						279,080,000
SPV Asset Facility I | Line of credit
Debt Instrument [Line Items]
Aggregate Principal Committed	925,000,000						625,000,000		$ 925,000,000.0			$ 625,000,000.0
Outstanding Principal	312,500,000						330,000,000
Amount Available	307,996,000						84,826,000
Unamortized Debt Issuance Costs	12,119,000						8,613,000
Net Carrying Value	300,381,000						321,387,000
SPV Asset Facility II | Line of credit
Debt Instrument [Line Items]
Aggregate Principal Committed	300,000,000	$ 300,000,000.0					300,000,000
Outstanding Principal	0						270,000,000
Amount Available	192,641,000						11,505,000
Unamortized Debt Issuance Costs	3,609,000						2,353,000
Net Carrying Value							267,647,000
Net Carrying Value	(3,609,000)
Athena CLO II | Unsecured debt investments
Debt Instrument [Line Items]
Aggregate Principal Committed	288,000,000						288,000,000
Outstanding Principal	288,000,000						288,000,000
Unamortized Debt Issuance Costs	2,263,000						2,404,000
Net Carrying Value	285,737,000						285,596,000
Athena CLO II | Secured Debt
Debt Instrument [Line Items]
Aggregate Principal Committed								$ 475,300,000
Athena CLO IV | Unsecured debt investments
Debt Instrument [Line Items]
Aggregate Principal Committed	240,000,000
Outstanding Principal	240,000,000
Unamortized Debt Issuance Costs	2,600,000
Athena CLO IV | Secured Debt
Debt Instrument [Line Items]
Aggregate Principal Committed			$ 399,700,000
Unamortized Debt Issuance Costs							0
2023A Notes | Unsecured debt investments
Debt Instrument [Line Items]
Aggregate Principal Committed	75,000,000						75,000,000
Outstanding Principal	75,000,000						75,000,000
Unamortized Debt Issuance Costs	720,000						856,000
Net Carrying Value	74,280,000						74,144,000
April 2029 Notes | Unsecured debt investments
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs							$ 0
April 2029 Notes | Secured Debt
Debt Instrument [Line Items]
Aggregate Principal Committed	700,000,000
Outstanding Principal	700,000,000
Unamortized Debt Issuance Costs	15,664,000
Net Carrying Value	$ 705,759,000