FAIR VALUE MEASUREMENTS - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Level 3 Inputs (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	$ 156,880	$ 166,420	$ 157,048	$ 164,948
Included in net investment income
Total foreign exchange gains (losses)	1	13	(3)	(6)
Purchases	0	1,666	141	1,366
Settlements	(895)		(1,120)
Balance at end of the period	$ 141,477	$ 170,680	$ 141,477	$ 170,680
Included in net investment income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net Investment Income	Net Investment Income	Net Investment Income	Net Investment Income
Included in net investment income
Included in earnings (loss)	$ 0	$ 62	$ 63	$ 124
Included in net realized and unrealized gains (losses) on investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized and unrealized gains (losses) on investments	Net realized and unrealized gains (losses) on investments	Net realized and unrealized gains (losses) on investments	Net realized and unrealized gains (losses) on investments
Included in net investment income
Included in earnings (loss)	$ (14,687)	$ 3,548	$ (14,687)	$ 4,257
Included in other income (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (loss)	Other income (loss)	Other income (loss)	Other income (loss)
Included in net investment income
Included in earnings (loss)	$ 178	$ (1,029)	$ 35	$ (9)
Direct Private Equity Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	59,964	67,532	59,905	66,780
Included in net investment income
Total foreign exchange gains (losses)	1	13	(3)	(6)
Purchases	0	0	0	0
Settlements	0		0
Balance at end of the period	45,278	71,155	45,278	71,155
Direct Private Equity Investments \| Included in net investment income
Included in net investment income
Included in earnings (loss)	0	62	63	124
Direct Private Equity Investments \| Included in net realized and unrealized gains (losses) on investments
Included in net investment income
Included in earnings (loss)	(14,687)	3,548	(14,687)	4,257
Direct Private Equity Investments \| Included in other income (loss)
Included in net investment income
Included in earnings (loss)	0	0	0	0
Term Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	97,433	100,000	97,658	100,000
Included in net investment income
Total foreign exchange gains (losses)	0	0	0	0
Purchases	0	0	0	0
Settlements	(794)		(1,019)
Balance at end of the period	96,639	100,000	96,639	100,000
Term Loans \| Included in net investment income
Included in net investment income
Included in earnings (loss)	0	0	0	0
Term Loans \| Included in net realized and unrealized gains (losses) on investments
Included in net investment income
Included in earnings (loss)	0	0	0	0
Term Loans \| Included in other income (loss)
Included in net investment income
Included in earnings (loss)	0	0	0	0
Other Assets and (Liabilities)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	(517)	(1,112)	(515)	(1,832)
Included in net investment income
Total foreign exchange gains (losses)	0	0	0	0
Purchases	0	1,666	141	1,366
Settlements	(101)		(101)
Balance at end of the period	(440)	(475)	(440)	(475)
Other Assets and (Liabilities) \| Included in net investment income
Included in net investment income
Included in earnings (loss)	0	0	0	0
Other Assets and (Liabilities) \| Included in net realized and unrealized gains (losses) on investments
Included in net investment income
Included in earnings (loss)	0	0	0	0
Other Assets and (Liabilities) \| Included in other income (loss)
Included in net investment income
Included in earnings (loss)	$ 178	$ (1,029)	$ 35	$ (9)

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- Definition

Amount of gain (loss) recognized in income from asset and liability measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
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- Definition

Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 101
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-101

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- Definition

Indicates line item in statement of income or comprehensive income that includes gain (loss) from asset (liability), measured at fair value using unobservable input (level 3).

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