INVESTMENTS (Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net Investment Income [Line Items]
Gross investment income	$ 107,528	$ 121,677	$ 259,517	$ 379,774
Investment expenses	(5,572)	(5,914)	(19,419)	(18,760)
Net investment income	101,956	115,763	240,098	361,014
Fixed maturities
Net Investment Income [Line Items]
Gross investment income	73,992	96,311	244,394	285,062
Other investments
Net Investment Income [Line Items]
Gross investment income	25,125	11,143	(14,574)	49,271
Equity securities
Net Investment Income [Line Items]
Gross investment income	1,871	2,232	6,258	7,757
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	3,609	3,984	11,322	10,735
Cash and cash equivalents
Net Investment Income [Line Items]
Gross investment income	2,491	7,034	9,814	20,974
Short-term investments
Net Investment Income [Line Items]
Gross investment income	$ 440	$ 973	$ 2,303	$ 5,975

The net gain or loss (both realized and unrealized) related to investments in certain entities that calculate net asset value per share and the amount after accretion (amortization) of discount (premium), of interest income and dividend income on nonoperating securities.

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The net gain or loss (both realized and unrealized) related to investments in certain entities that calculate net asset value per share and the amount after accretion (amortization) of discount (premium) of interest income and dividend income on nonoperating securities, net of investment expense.

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Amount of expenses related to the generation of investment income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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