Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount excluding accrued interest, of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

INVESTMENTS - Fixed Maturities Available for Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Available for sale
Amortized cost	$ 12,587,327		$ 12,176,473
Allowance for expected credit losses	(8,933)	$ (10,551)	(11,733)	$ (10,504)	$ (7,294)	$ (313)
Gross unrealized gains	7,664		18,742
Gross unrealized losses	(862,690)		(856,588)
Fair value	11,723,368		11,326,894
U.S. government and agency
Available for sale
Amortized cost	2,976,548		2,731,733
Allowance for expected credit losses	0		0
Gross unrealized gains	117		5,386
Gross unrealized losses	(116,032)		(97,789)
Fair value	2,860,633		2,639,330
Non-U.S. government
Available for sale
Amortized cost	718,298		612,546
Allowance for expected credit losses	(17)		0
Gross unrealized gains	854		2,395
Gross unrealized losses	(48,880)		(52,912)
Fair value	670,255		562,029
Corporate debt
Available for sale
Amortized cost	4,610,179		4,680,798
Allowance for expected credit losses	(8,684)		(11,521)
Gross unrealized gains	5,737		5,269
Gross unrealized losses	(377,369)		(418,990)
Fair value	4,229,863		4,255,556
Agency RMBS
Available for sale
Amortized cost	1,707,603		1,297,423
Allowance for expected credit losses	0		0
Gross unrealized gains	44		4,663
Gross unrealized losses	(166,142)		(99,301)
Fair value	1,541,505		1,202,785
CMBS
Available for sale
Amortized cost	947,370		1,029,863
Allowance for expected credit losses	0		0
Gross unrealized gains	36		60
Gross unrealized losses	(82,355)		(82,145)
Fair value	865,051		947,778
Non-agency RMBS
Available for sale
Amortized cost	155,437		151,907
Allowance for expected credit losses	(133)		(123)
Gross unrealized gains	123		275
Gross unrealized losses	(17,623)		(18,525)
Fair value	137,804		133,534
ABS
Available for sale
Amortized cost	1,304,644		1,499,728
Allowance for expected credit losses	(38)		(35)
Gross unrealized gains	711		555
Gross unrealized losses	(38,449)		(70,721)
Fair value	1,266,868		1,429,527
Municipals
Available for sale
Amortized cost	167,248		172,475
Allowance for expected credit losses	(61)		(54)
Gross unrealized gains	42		139
Gross unrealized losses	(15,840)		(16,205)
Fair value	$ 151,389		$ 156,355