FAIR VALUE (Available-for-Sale Financial Instruments Measured at Fair Value) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	$ 540,443	$ 526,265
Equity securities, at fair value	13,108	20,039
Total investments, at fair value	553,551	546,304
United States Government Obligations and Authorities
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	191,533	194,193
Obligations of States and Political Subdivisions
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	22,226	24,020
Corporate
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	295,745	278,302
International
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	30,939	29,750
Level 1
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	36,115	83,764
Equity securities, at fair value	10,724	17,361
Total investments, at fair value	46,839	101,125
Level 1 \| United States Government Obligations and Authorities
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	36,115	83,764
Level 1 \| Obligations of States and Political Subdivisions
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	0	0
Level 1 \| Corporate
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	0	0
Level 1 \| International
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	0	0
Level 2
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	504,328	442,501
Equity securities, at fair value	2,384	2,678
Total investments, at fair value	506,712	445,179
Level 2 \| United States Government Obligations and Authorities
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	155,418	110,429
Level 2 \| Obligations of States and Political Subdivisions
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	22,226	24,020
Level 2 \| Corporate
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	295,745	278,302
Level 2 \| International
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	30,939	29,750
Level 3
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	0	0
Equity securities, at fair value	0	0
Total investments, at fair value	0	0
Level 3 \| United States Government Obligations and Authorities
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	0	0
Level 3 \| Obligations of States and Political Subdivisions
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	0	0
Level 3 \| Corporate
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	0	0
Level 3 \| International
Investments, Debt and Equity Securities [Abstract]
Debt securities - available-for-sale, at fair value:	$ 0	$ 0

Amount of 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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