INVESTMENTS (Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net Investment Income [Line Items]
Gross investment income	$ 51,560	$ 144,734	$ 151,988	$ 258,099
Investment expenses	(6,520)	(6,785)	(13,848)	(12,845)
Net investment income	45,040	137,949	138,140	245,254
Fixed maturities
Net Investment Income [Line Items]
Gross investment income	80,459	97,370	170,402	188,752
Other investments
Net Investment Income [Line Items]
Gross investment income	(37,580)	31,232	(39,700)	38,128
Equity securities
Net Investment Income [Line Items]
Gross investment income	2,263	3,197	4,387	5,525
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	3,660	3,689	7,713	6,752
Cash and cash equivalents
Net Investment Income [Line Items]
Gross investment income	2,392	8,138	7,323	13,940
Short-term investments
Net Investment Income [Line Items]
Gross investment income	$ 366	$ 1,108	$ 1,863	$ 5,002

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.

+ References

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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

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-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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