FAIR VALUE MEASUREMENTS - Summary of Changes in Level 3 for Financial Instruments Measured at Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Change in unrealized gain/(losses)	$ 16,257	$ 28,092
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	153,325	91,093
Transfers into Level 3	0	0
Transfers out of Level 3	0	(10,200)
Included in net income	16,153	45,472
Included in OCI	(9,014)	(594)
Purchases	110,121	63,560
Sales	0	(26,980)
Settlements/ distributions	(10,307)	(9,026)
Closing balance	260,278	153,325
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	5,630	9,122
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income	(3,542)	(2,742)
Included in OCI	0	0
Purchases	0	0
Sales	0	0
Settlements/ distributions	(2,088)	(750)
Closing balance	0	5,630
Change in unrealized gains/(losses)	$ 0	$ (1,769)
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net investment income, Net Investment Gain (Loss)	Net investment income, Net Investment Gain (Loss)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net investment income, Net Investment Gain (Loss)	Net investment income, Net Investment Gain (Loss)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Unrealized gains (losses) arising during the year	Unrealized gains (losses) arising during the year
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net investment income, Net Investment Gain (Loss)	Net investment income, Net Investment Gain (Loss)
FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfOtherComprehensiveIncomeExtensibleListNotDisclosedFlag	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent
Fixed maturities
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Change in unrealized gain/(losses)	$ 0	$ 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	42,894	14,909
Transfers into Level 3	0	0
Transfers out of Level 3	0	(10,200)
Included in net income	(104)	0
Included in OCI	(9,014)	(594)
Purchases	90,130	41,800
Sales	0	0
Settlements/ distributions	(4,802)	(3,021)
Closing balance	119,104	42,894
Other investments
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Change in unrealized gain/(losses)	16,257	28,092
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	110,431	76,184
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income	16,257	45,472
Included in OCI	0	0
Purchases	19,991	21,760
Sales	0	(26,980)
Settlements/ distributions	(5,505)	(6,005)
Closing balance	141,174	110,431
Corporate debt | Fixed maturities
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Change in unrealized gain/(losses)	0	0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	42,894	2,504
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income	(104)	0
Included in OCI	(9,014)	(642)
Purchases	90,130	41,800
Sales	0	0
Settlements/ distributions	(4,802)	(768)
Closing balance	119,104	42,894
CMBS | Fixed maturities
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Change in unrealized gain/(losses)	0	0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	0	1,740
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income	0	0
Included in OCI	0	13
Purchases	0	0
Sales	0	0
Settlements/ distributions	0	(1,753)
Closing balance	0	0
ABS | Fixed maturities
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Change in unrealized gain/(losses)	0	0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	0	10,665
Transfers into Level 3	0	0
Transfers out of Level 3	0	(10,200)
Included in net income	0	0
Included in OCI	0	35
Purchases	0	0
Sales	0	0
Settlements/ distributions	0	(500)
Closing balance	0	0
CLO-Equities | Other investments
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Change in unrealized gain/(losses)	2,611	2,819
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	5,910	6,173
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income	2,611	2,819
Included in OCI	0	0
Purchases	0	0
Sales	0	0
Settlements/ distributions	(3,505)	(3,082)
Closing balance	5,016	5,910
Other privately held investments | Other investments
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Change in unrealized gain/(losses)	13,646	25,273
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	104,521	70,011
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income	13,646	42,653
Included in OCI	0	0
Purchases	19,991	21,760
Sales	0	(26,980)
Settlements/ distributions	(2,000)	(2,923)
Closing balance	136,158	104,521
Derivative instruments
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance	5,630	9,122
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income	(3,542)	(2,742)
Included in OCI	0	0
Purchases	0	0
Sales	0	0
Settlements/ distributions	(2,088)	(750)
Closing balance	0	5,630
Change in unrealized gains/(losses)	$ 0	$ (1,769)