Organization	12 Months Ended
Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Oaktree Specialty Lending Corporation (together with its consolidated subsidiaries, the "Company") is a specialty finance company that looks to provide customized, one-stop credit solutions to companies with limited access to public or syndicated capital markets. The Company was formed in late 2007 and operates as a closed-end, externally managed, non-diversified management investment company that has elected to be regulated as a Business Development Company under the Investment Company Act. The Company has qualified and elected to be treated as a regulated investment company ("RIC") under the Internal Revenue Code of 1986, as amended (the "Code"), for U.S. federal income tax purposes. The Company's investment objective is to generate current income and capital appreciation by providing companies with flexible and innovative financing solutions, including first and second lien loans, unsecured and mezzanine loans, bonds, preferred equity and certain equity co-investments. The Company may also seek to generate capital appreciation and income through secondary investments at discounts to par in either private or syndicated transactions. The Company is externally managed by Oaktree Fund Advisors, LLC ("Oaktree"), pursuant to an investment advisory agreement between the Company and Oaktree (as amended and restated, the "Investment Advisory Agreement"). Oaktree is an affiliate of Oaktree Capital Management, L.P. ("OCM"), the Company's external investment adviser from October 17, 2017 through May 3, 2020. Oaktree Fund Administration, LLC ("Oaktree Administrator"), a subsidiary of OCM, provides certain administrative and other services necessary for the Company to operate pursuant to an administration agreement between the Company and Oaktree Administrator (the "Administration Agreement"). See Note 10. In 2019, Brookfield Corporation (f/k/a Brookfield Asset Management Inc.) ("Brookfield") acquired a majority economic interest in Oaktree Capital Group, LLC. Oaktree and its affiliates operate as an independent business within Brookfield, with their own product offerings and investment, marketing and support teams. On March 19, 2021, the Company acquired Oaktree Strategic Income Corporation (“OCSI”), pursuant to that certain Agreement and Plan of Merger (the “OCSI Merger Agreement”), dated as of October 28, 2020, by and among OCSI, the Company, Lion Merger Sub, Inc., a wholly-owned subsidiary of the Company, and, solely for the limited purposes set forth therein, Oaktree. Pursuant to the OCSI Merger Agreement, OCSI was merged with and into the Company in a two-step transaction, with the Company as the surviving company (the "OCSI Merger”). On January 23, 2023, the Company acquired Oaktree Strategic Income II, Inc. (“OSI2”) pursuant to that certain Agreement and Plan of Merger (the “OSI2 Merger Agreement”), dated as of September 14, 2022, by and among OSI2, the Company, Project Superior Merger Sub, Inc., a wholly-owned subsidiary of the Company, and, solely for the limited purposes set forth therein, Oaktree. Pursuant to the OSI2 Merger Agreement, OSI2 was merged with and into the Company in a two-step transaction with the Company as the surviving company (the “OSI2 Merger”). For further information, see Note 14 "Merger with OSI2."

Oaktree Specialty Lending Corporation (together with its consolidated subsidiaries, the "Company") is a specialty finance company that looks to provide customized, one-stop credit solutions to companies with limited access to public or syndicated capital markets. The Company was formed in late 2007 and operates as a closed-end, externally managed, non-diversified management investment company that has elected to be regulated as a Business Development Company under the Investment Company Act. The Company has qualified and elected to be treated as a regulated investment company ("RIC") under the Internal Revenue Code of 1986, as amended (the "Code"), for U.S. federal income tax purposes.

The Company's investment objective is to generate current income and capital appreciation by providing companies with flexible and innovative financing solutions, including first and second lien loans, unsecured and mezzanine loans, bonds, preferred equity and certain equity co-investments. The Company may also seek to generate capital appreciation and income through secondary investments at discounts to par in either private or syndicated transactions.

The Company is externally managed by Oaktree Fund Advisors, LLC ("Oaktree"), pursuant to an investment advisory agreement between the Company and Oaktree (as amended and restated, the "Investment Advisory Agreement"). Oaktree is an affiliate of Oaktree Capital Management, L.P. ("OCM"), the Company's external investment adviser from October 17, 2017 through May 3, 2020. Oaktree Fund Administration, LLC ("Oaktree Administrator"), a subsidiary of OCM, provides certain administrative and other services necessary for the Company to operate pursuant to an administration agreement between the Company and Oaktree Administrator (the "Administration Agreement"). See Note 10. In 2019, Brookfield Corporation (f/k/a Brookfield Asset Management Inc.) ("Brookfield") acquired a majority economic interest in Oaktree Capital Group, LLC. Oaktree and its affiliates operate as an independent business within Brookfield, with their own product offerings and investment, marketing and support teams.

On March 19, 2021, the Company acquired Oaktree Strategic Income Corporation (“OCSI”), pursuant to that certain Agreement and Plan of Merger (the “OCSI Merger Agreement”), dated as of October 28, 2020, by and among OCSI, the Company, Lion Merger Sub, Inc., a wholly-owned subsidiary of the Company, and, solely for the limited purposes set forth therein, Oaktree. Pursuant to the OCSI Merger Agreement, OCSI was merged with and into the Company in a two-step transaction, with the Company as the surviving company (the "OCSI Merger”).

On January 23, 2023, the Company acquired Oaktree Strategic Income II, Inc. (“OSI2”) pursuant to that certain Agreement and Plan of Merger (the “OSI2 Merger Agreement”), dated as of September 14, 2022, by and among OSI2, the Company, Project Superior Merger Sub, Inc., a wholly-owned subsidiary of the Company, and, solely for the limited purposes set forth therein, Oaktree. Pursuant to the OSI2 Merger Agreement, OSI2 was merged with and into the Company in a two-step transaction with the Company as the surviving company (the “OSI2 Merger”). For further information, see Note 14 "Merger with OSI2."