v3.23.3

Portfolio Investments - Schedule of Financial Instruments Disclosed, but Carried at Fair Value (Details) - USD ($) $ in Thousands | Sep. 30, 2023 | Sep. 30, 2022
--- | --- | ---
Schedule of Investments [Line Items] |  |
Carrying Value | $ 1,600,731 | $ 1,301,043
Fair Value | 1,588,201 | 1,277,105
Syndicated Facility |  |
Schedule of Investments [Line Items] |  |
Carrying Value | 430,000 | 540,000
Fair Value | 430,000 | 540,000
OSI2 Citibank Facility |  |
Schedule of Investments [Line Items] |  |
Carrying Value | 280,000 |
Fair Value | 280,000 |
Citibank Facility |  |
Schedule of Investments [Line Items] |  |
Carrying Value |  | 160,000
Fair Value |  | 160,000
2025 Notes |  |
Schedule of Investments [Line Items] |  |
Carrying Value | 298,241 | 296,991
Fair Value | 286,437 | 283,077
2027 Notes |  |
Schedule of Investments [Line Items] |  |
Carrying Value | 306,412 | 304,052
Fair Value | 301,784 | 294,028
2029 Notes |  |
Schedule of Investments [Line Items] |  |
Carrying Value | 286,078 |
Fair Value | 289,980 |
Level 1 |  |
Schedule of Investments [Line Items] |  |
Fair Value | 0 | 0
Level 1 | Syndicated Facility |  |
Schedule of Investments [Line Items] |  |
Fair Value | 0 | 0
Level 1 | OSI2 Citibank Facility |  |
Schedule of Investments [Line Items] |  |
Fair Value | 0 |
Level 1 | Citibank Facility |  |
Schedule of Investments [Line Items] |  |
Fair Value |  | 0
Level 1 | 2025 Notes |  |
Schedule of Investments [Line Items] |  |
Fair Value | 0 | 0
Level 1 | 2027 Notes |  |
Schedule of Investments [Line Items] |  |
Fair Value | 0 | 0
Level 1 | 2029 Notes |  |
Schedule of Investments [Line Items] |  |
Fair Value | 0 |
Level 2 |  |
Schedule of Investments [Line Items] |  |
Fair Value | 878,201 | 577,105
Level 2 | Syndicated Facility |  |
Schedule of Investments [Line Items] |  |
Fair Value | 0 | 0
Level 2 | OSI2 Citibank Facility |  |
Schedule of Investments [Line Items] |  |
Fair Value | 0 |
Level 2 | Citibank Facility |  |
Schedule of Investments [Line Items] |  |
Fair Value |  | 0
Level 2 | 2025 Notes |  |
Schedule of Investments [Line Items] |  |
Fair Value | 286,437 | 283,077
Level 2 | 2027 Notes |  |
Schedule of Investments [Line Items] |  |
Fair Value | 301,784 | 294,028
Level 2 | 2029 Notes |  |
Schedule of Investments [Line Items] |  |
Fair Value | 289,980 |
Level 3 |  |
Schedule of Investments [Line Items] |  |
Fair Value | 710,000 | 700,000
Level 3 | Syndicated Facility |  |
Schedule of Investments [Line Items] |  |
Fair Value | 430,000 | 540,000
Level 3 | OSI2 Citibank Facility |  |
Schedule of Investments [Line Items] |  |
Fair Value | 280,000 |
Level 3 | Citibank Facility |  |
Schedule of Investments [Line Items] |  |
Fair Value |  | 160,000
Level 3 | 2025 Notes |  |
Schedule of Investments [Line Items] |  |
Fair Value | 0 | 0
Level 3 | 2027 Notes |  |
Schedule of Investments [Line Items] |  |
Fair Value | 0 | $ 0
Level 3 | 2029 Notes |  |
Schedule of Investments [Line Items] |  |
Fair Value | $ 0 |

X
- Definition Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -SubTopic 10 -Topic 210 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 69B -Publisher FASB -URI https://asc.fasb.org//1943274/2147481568/470-20-55-69B Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 69C -Publisher FASB -URI https://asc.fasb.org//1943274/2147481568/470-20-55-69C Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1D -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481139/470-20-50-1D Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)(a)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481139/470-20-50-4 + Details
Name: | us-gaap_LongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. + References No definition available. + Details
Name: | us-gaap_LongTermDebtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column A)(Footnote 2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 4)(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column A)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column B)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column A)(Footnote 1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column A)(Footnote 2)(i)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column A)(Footnote 2)(ii)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column A)(Footnote 4)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 5)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 6)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column B)(Footnote 7)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 8)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 8)(a)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 8)(a)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 8)(a)(3)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 8)(b)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 8)(b)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 8)(c)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 22: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 9)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 23: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 10)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column B)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column D)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 28: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 1)(a)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 29: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 1)(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 30: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 31: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 3)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 32: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 4)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 33: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 4)(a)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 34: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 6)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 35: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 7)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 36: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 9)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 37: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column B)(Footnote 10)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 38: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 11)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 39: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 11)(a)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 40: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 11)(a)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 41: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 11)(a)(3)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 42: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 11)(b)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 43: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 11)(b)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 44: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 11)(c)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 45: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 12)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 46: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 13)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 47: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 48: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column B)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 49: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 50: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(a)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 51: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(a)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 52: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(a)(3)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 53: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 54: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(3)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 55: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(4)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 56: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(5)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 57: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 58: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 3)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 59: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)(Footnote 4)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 60: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)(Footnote 5)(a)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 61: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)(Footnote 7)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 62: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)(Footnote 8)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 63: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)(Footnote 9)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 64: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 19 -Subparagraph (1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-19 Reference 65: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 19 -Subparagraph (3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-19 + Details
Name: | us-gaap_ScheduleOfInvestmentsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=ocsl_SyndicatedFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=ocsl_OSI2CitibankFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=ocsl_CitibankFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=ocsl_A2025NotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=ocsl_A2027NotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=ocsl_A2029NotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |