FAIR VALUE MEASUREMENTS - 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, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	$ 166,420	$ 161,114	$ 164,948	$ 158,496
Total foreign exchange gains (losses)	13		(6)	(10)
Purchases	1,666	20,755	1,366	30,474
Settlements				(455)
Balance at end of the period	170,680	178,546	170,680	178,546
Included in net investment income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings	62	0	124	605
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	3,548	(3,603)	4,257	(11,753)
Included in other income (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings	(1,029)	280	(9)	1,189
Direct private equity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	67,532	80,213	66,780	88,373
Total foreign exchange gains (losses)	13		(6)	(10)
Purchases	0	5,000	0	5,000
Settlements				0
Balance at end of the period	71,155	81,610	71,155	81,610
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	62	0	124	0
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	3,548	(3,603)	4,257	(11,753)
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	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	85,000	100,000	74,850
Total foreign exchange gains (losses)	0		0	0
Purchases	0	15,000	0	25,000
Settlements				(455)
Balance at end of the period	100,000	100,000	100,000	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	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	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	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	(1,112)	(4,099)	(1,832)	(4,727)
Total foreign exchange gains (losses)	0		0	0
Purchases	1,666	755	1,366	474
Settlements				0
Balance at end of the period	(475)	(3,064)	(475)	(3,064)
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	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	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	$ (1,029)	$ 280	$ (9)	$ 1,189