FAIR VALUE MEASUREMENTS (Changes in Level 3 for Financial Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	$ 66,371	$ 130,020	$ 59,283	$ 152,468
Transfers into Level 3	0	0	9,185	0
Transfers out of Level 3	0	(11,564)	0	(32,733)
Included in net income	(2,398)	14,264	(3,165)	14,650
Included in OCI	616	342	118	1,271
Purchases	55	0	482	12,250
Sales	0	(33,458)	0	(39,005)
Settlements/ distributions	(546)	(3,834)	(1,805)	(13,131)
Closing balance	64,098	95,770	64,098	95,770
Change in unrealized investment gains/(losses)	(2,398)	1,600	(3,165)	2,682
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	20,164	10,233	9,672	10,299
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	(375)	29	10,117	(37)
Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/ distributions	(9,971)	0	(9,971)	0
Closing balance	9,818	10,262	9,818	10,262
Change in unrealized investment gains/(losses)	(346)	29	146	(37)
Other liabilities | Derivative instruments
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	20,164	10,233	9,672	10,299
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	(375)	29	10,117	(37)
Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/ distributions	(9,971)	0	(9,971)	0
Closing balance	9,818	10,262	9,818	10,262
Change in unrealized investment gains/(losses)	(346)	29	146	(37)
Fixed maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	16,137	64,313	8,021	86,679
Transfers into Level 3	0	0	9,185	0
Transfers out of Level 3	0	(11,564)	0	(32,733)
Included in net income	0	(763)	0	(1,459)
Included in OCI	616	342	118	1,271
Purchases	0	0	0	9,750
Sales	0	(31)	0	(5,578)
Settlements/ distributions	(18)	(2,777)	(589)	(8,410)
Closing balance	16,735	49,520	16,735	49,520
Change in unrealized investment gains/(losses)	0	0	0	0
Fixed maturities | Corporate debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	2,245	41,125	2,297	49,012
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	0	(763)	0	(1,459)
Included in OCI	53	309	1	933
Purchases	0	0	0	0
Sales	0	(31)	0	(5,578)
Settlements/ distributions	0	(1,503)	0	(3,771)
Closing balance	2,298	39,137	2,298	39,137
Change in unrealized investment gains/(losses)	0	0	0	0
Fixed maturities | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	4,371	11,145	5,235	19,134
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	(4,767)
Included in net income	0	0	0	0
Included in OCI	81	21	(212)	164
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/ distributions	(18)	(1,274)	(589)	(4,639)
Closing balance	4,434	9,892	4,434	9,892
Change in unrealized investment gains/(losses)	0	0	0	0
Fixed maturities | Non-agency RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	9,185	0	0	0
Transfers into Level 3	0	0	9,185	0
Transfers out of Level 3	0	0	0	0
Included in net income	0	0	0	0
Included in OCI	377	0	377	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/ distributions	0	0	0	0
Closing balance	9,562	0	9,562	0
Change in unrealized investment gains/(losses)	0	0	0	0
Fixed maturities | ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	336	12,043	489	18,533
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	(11,564)	0	(27,966)
Included in net income	0	0	0	0
Included in OCI	105	12	(48)	174
Purchases	0	0	0	9,750
Sales	0	0	0	0
Settlements/ distributions	0	0	0	0
Closing balance	441	491	441	491
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	50,234	65,707	51,262	65,789
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	(2,398)	15,027	(3,165)	16,109
Included in OCI	0	0	0	0
Purchases	55	0	482	2,500
Sales	0	(33,427)	0	(33,427)
Settlements/ distributions	(528)	(1,057)	(1,216)	(4,721)
Closing balance	47,363	46,250	47,363	46,250
Change in unrealized investment gains/(losses)	(2,398)	1,600	(3,165)	2,682
Other investments | CLO-Equities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	12,793	18,022	14,328	21,271
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	(2,322)	833	(3,169)	1,248
Included in OCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/ distributions	(528)	(1,057)	(1,216)	(4,721)
Closing balance	9,943	17,798	9,943	17,798
Change in unrealized investment gains/(losses)	(2,322)	833	(3,169)	1,248
Other investments | Other privately held investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	37,441	47,685	36,934	44,518
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Included in net income	(76)	14,194	4	14,861
Included in OCI	0	0	0	0
Purchases	55	0	482	2,500
Sales	0	(33,427)	0	(33,427)
Settlements/ distributions	0	0	0	0
Closing balance	37,420	28,452	37,420	28,452
Change in unrealized investment gains/(losses)	$ (76)	$ 767	$ 4	$ 1,434