INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Income Tax Disclosure [Abstract]
Excise taxes	$ 0.0	$ 0.3	$ 0.4	$ 0.5
Cost of investments, income tax purposes	4,480.4		4,480.4		$ 3,150.7
Unrealized appreciation (depreciation)	(9.8)		(9.8)		(21.2)
Unrealized gross appreciation	118.9		118.9		93.7
Unrealized gross depreciation	128.7		128.7		114.9
Deferred tax liabilities	$ 2.6		$ 2.6		$ 2.4

Amount of deferred tax liability attributable to taxable temporary differences from investments (excludes investments in subsidiaries and equity method investments).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-6

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The amount of excise and sales taxes included in sales and revenues, which are then deducted as a cost of sales. Includes excise taxes, which are applied to specific types of transactions or items (such as gasoline or alcohol); and sales, use and value added taxes, which are applied to a broad class of revenue-producing transactions involving a wide range of goods and services.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(1))
-Publisher FASB
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Amount of cost of investment for federal income tax purpose.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(h)(2)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3

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Amount of cumulative increase in investment from unrealized gain when value exceeds cost for federal income tax purpose.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(h)(2)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3

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Amount of cumulative decrease in investment from unrealized loss when cost for federal income tax purpose exceeds value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(h)(2)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3

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Amount of cumulative increase (decrease) in investment from unrealized gain (loss) when value exceeds (is less than) cost for federal income tax purpose.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(h)(2)(iii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3

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