FAIR VALUE MEASUREMENTS (Changes in Level 3 for Financial Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	$ 78,537	$ 66,371	$ 91,093	$ 59,283
Transfers into Level 3	19,382	0	25,566	9,185
Transfers out of Level 3	(7,004)	0	(16,207)	0
Included in net income	1,413	(2,398)	20,462	(3,165)
Included in OCI	26	616	(29)	118
Purchases	16,300	55	16,573	482
Sales	0	0	(26,980)	0
Settlements/ distributions	(1,580)	(546)	(3,404)	(1,805)
Closing balance	107,074	64,098	107,074	64,098
Change in unrealized investment gains/(losses)	1,413	(2,398)	3,081	(3,165)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	8,462	20,164	9,122	9,672
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	(345)	(375)	(1,005)	10,117
Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/ distributions	0	(9,971)	0	(9,971)
Closing balance	8,117	9,818	8,117	9,818
Change in unrealized investment gains/(losses)	(345)	(346)	(1,005)	146
Other liabilities | Derivative instruments
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	8,462	20,164	9,122	9,672
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	(345)	(375)	(1,005)	10,117
Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/ distributions	0	(9,971)	0	(9,971)
Closing balance	8,117	9,818	8,117	9,818
Change in unrealized investment gains/(losses)	(345)	(346)	(1,005)	146
Fixed maturities, available for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	10,485	16,137	14,909	8,021
Transfers into Level 3	19,382	0	25,566	9,185
Transfers out of Level 3	(7,004)	0	(16,207)	0
Included in net income	0	0	0	0
Included in OCI	26	616	(29)	118
Purchases	13,300	0	13,300	0
Sales	0	0	0	0
Settlements/ distributions	(903)	(18)	(2,253)	(589)
Closing balance	35,286	16,735	35,286	16,735
Change in unrealized investment gains/(losses)	0	0	0	0
Fixed maturities, available for sale | Corporate debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	2,405	2,245	2,504	2,297
Transfers into Level 3	7,000	0	7,000	0
Transfers out of Level 3	0	0	0	0
Included in net income	0	0	0	0
Included in OCI	21	53	(78)	1
Purchases	13,300	0	13,300	0
Sales	0	0	0	0
Settlements/ distributions	0	0	0	0
Closing balance	22,726	2,298	22,726	2,298
Change in unrealized investment gains/(losses)	0	0	0	0
Fixed maturities, available for sale | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	905	4,371	1,740	5,235
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	0	0	0	0
Included in OCI	(2)	81	13	(212)
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/ distributions	(903)	(18)	(1,753)	(589)
Closing balance	0	4,434	0	4,434
Change in unrealized investment gains/(losses)	0	0	0	0
Fixed maturities, available for sale | Non-agency RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance		9,185		0
Transfers into Level 3		0		9,185
Transfers out of Level 3		0		0
Included in net income		0		0
Included in OCI		377		377
Purchases		0		0
Sales		0		0
Settlements/ distributions		0		0
Closing balance		9,562		9,562
Change in unrealized investment gains/(losses)		0		0
Fixed maturities, available for sale | ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	7,175	336	10,665	489
Transfers into Level 3	12,382	0	18,566	0
Transfers out of Level 3	(7,004)	0	(16,207)	0
Included in net income	0	0	0	0
Included in OCI	7	105	36	(48)
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/ distributions	0	0	(500)	0
Closing balance	12,560	441	12,560	441
Change in unrealized investment gains/(losses)	0	0	0	0
Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	68,052	50,234	76,184	51,262
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	1,413	(2,398)	20,462	(3,165)
Included in OCI	0	0	0	0
Purchases	3,000	55	3,273	482
Sales	0	0	(26,980)	0
Settlements/ distributions	(677)	(528)	(1,151)	(1,216)
Closing balance	71,788	47,363	71,788	47,363
Change in unrealized investment gains/(losses)	1,413	(2,398)	3,081	(3,165)
Other investments | CLO-Equities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	6,269	12,793	6,173	14,328
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	1,410	(2,322)	1,980	(3,169)
Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/ distributions	(677)	(528)	(1,151)	(1,216)
Closing balance	7,002	9,943	7,002	9,943
Change in unrealized investment gains/(losses)	1,410	(2,322)	1,980	(3,169)
Other investments | Other privately held investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	61,783	37,441	70,011	36,934
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	3	(76)	18,482	4
Included in OCI	0	0	0	0
Purchases	3,000	55	3,273	482
Sales	0	0	(26,980)	0
Settlements/ distributions	0	0	0	0
Closing balance	64,786	37,420	64,786	37,420
Change in unrealized investment gains/(losses)	$ 3	$ (76)	$ 1,101	$ 4