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		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	$ 170,680	$ 178,546	$ 164,948	$ 158,496
Total foreign exchange gains (losses)	(17)	(50)	(23)	(60)
Purchases	471	(50)	1,837	30,424
Settlements	(1,124)		(1,124)	(455)
Balance at end of the period	165,846	167,352	165,846	167,352
Included in net investment income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings (loss)	63	125	187	730
Included in net realized and unrealized gains (losses) on investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings (loss)	(3,686)	(11,762)	571	(23,515)
Included in other income (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings (loss)	(541)	543	(550)	1,732
Direct private equity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	71,155	81,610	66,780	88,373
Total foreign exchange gains (losses)	(17)	(50)	(23)	(60)
Purchases	0	0	0	5,000
Settlements	0		0	0
Balance at end of the period	67,515	69,923	67,515	69,923
Direct private equity investments | Included in net investment income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings (loss)	63	125	187	125
Direct private equity investments | Included in net realized and unrealized gains (losses) on investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings (loss)	(3,686)	(11,762)	571	(23,515)
Direct private equity investments | Included in other income (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
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	100,000	100,000	100,000	74,850
Total foreign exchange gains (losses)	0	0	0	0
Purchases	0	0	0	25,000
Settlements	(1,124)		(1,124)	(455)
Balance at end of the period	98,876	100,000	98,876	100,000
Term loans | Included in net investment income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings (loss)	0	0	0	605
Term loans | Included in net realized and unrealized gains (losses) on investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings (loss)	0	0	0	0
Term loans | Included in other income (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
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	(475)	(3,064)	(1,832)	(4,727)
Total foreign exchange gains (losses)	0	0	0	0
Purchases	471	(50)	1,837	424
Settlements	0		0	0
Balance at end of the period	(545)	(2,571)	(545)	(2,571)
Other assets  and (liabilities) | Included in net investment income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings (loss)	0	0	0	0
Other assets  and (liabilities) | Included in net realized and unrealized gains (losses) on investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings (loss)	0	0	0	0
Other assets  and (liabilities) | Included in other income (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings (loss)	$ (541)	$ 543	$ (550)	$ 1,732