Agreements and Related Party Transactions (Details) $ in Thousands									3 Months Ended		9 Months Ended		48 Months Ended
	Jul. 28, 2023 USD ($)	May 08, 2023 component	Dec. 14, 2022 USD ($)	Jul. 18, 2022 USD ($)	Jul. 01, 2022 USD ($)	May 03, 2022	May 18, 2021	Sep. 24, 2019 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)
Related Party Transaction [Line Items]
Management fees									$ 47,796	$ 46,886	$ 143,911	$ 141,172
Performance based incentive fees									40,314	31,134	117,640	83,630
Affiliated entity | Administration Agreement
Related Party Transaction [Line Items]
Contract term							2 years
Written notice for contract termination, term						60 days
Affiliated entity | Administration Agreement, Costs And Expenses Reimbursable
Related Party Transaction [Line Items]
Amount of transaction									2,000	1,500	5,900	4,500
Affiliated entity | Investment Advisory Agreement
Related Party Transaction [Line Items]
Contract term							2 years
Written notice for contract termination, term		60 days
Required term of written notice for contract termination for certain circumstances		120 days
Incentive fee components | component		2
Affiliated entity | Investment Advisory Agreement, Management Fee - Average Gross Assets
Related Party Transaction [Line Items]
Base rate		1.50%
Affiliated entity | Investment Advisory Agreement, Management Fee - Asset Coverage Ratio Threshold
Related Party Transaction [Line Items]
Base rate		200.00%
Affiliated entity | Investment Advisory Agreement, Management Fee - Average Gross Assets Below Asset Coverage Ratio
Related Party Transaction [Line Items]
Base rate		1.00%
Affiliated entity | Investment Management Agreement - Incentive Rate, Pre-Incentive Fee Net Investment Income
Related Party Transaction [Line Items]
Incentive rate		100.00%
Affiliated entity | Investment Management Agreement - Incentive Rate, Quarterly Hurdle Rate
Related Party Transaction [Line Items]
Incentive rate		1.50%
Affiliated entity | Investment Advisory Agreement - Incentive Rate, Pre-Incentive Fee Net Investment Income Threshold
Related Party Transaction [Line Items]
Incentive rate		17.50%
Affiliated entity | Investment Advisory Agreement - Incentive Rate, Quarterly Threshold
Related Party Transaction [Line Items]
Incentive rate		1.82%
Affiliated entity | Investment Management Agreement - Incentive Rate, Realized Capital Gains
Related Party Transaction [Line Items]
Incentive rate						17.50%
Affiliated entity | Management Fee
Related Party Transaction [Line Items]
Management fees									47,800	46,900	143,900	141,200
Affiliated entity | Performance Based Incentive Fee
Related Party Transaction [Line Items]
Performance based incentive fees									40,300	$ 31,100	117,600	$ 83,600
Affiliated entity | Commitment To Indirectly Owned Subsidiary
Related Party Transaction [Line Items]
Amount of transaction								$ 50,000					$ 450,000
Affiliated entity | Commitment To Amergin AssetCo
Related Party Transaction [Line Items]
Amount of transaction	$ 110,000				$ 90,000
Affiliated entity | Equity Commitment To Amergin AssetCo
Related Party Transaction [Line Items]
Amount of transaction	74,400
Affiliated entity | Debt Commitment To Amergin AssetCo
Related Party Transaction [Line Items]
Amount of transaction	$ 35,600
Affiliated entity | Equity Commitment To Fifth Season
Related Party Transaction [Line Items]
Amount of transaction				$ 15,900					$ 12,300		33,300
Affiliated entity | Equity Commitment To LSI Financing
Related Party Transaction [Line Items]
Amount of transaction			$ 6,200								$ 15,000