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

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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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Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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FAIR VALUE - (Financial Instruments Measured at Fair Value) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Fair value	$ 488,210	$ 526,265
Equity securities, at fair value	3,157	20,039
Total investments, at fair value	491,367	546,304
Fair value transfers	0	0	$ 0
United States government obligations and authorities
Investments, Debt and Equity Securities [Abstract]
Fair value	171,775	194,193
Obligations of states and political subdivisions
Investments, Debt and Equity Securities [Abstract]
Fair value	22,264	24,020
Corporate securities
Investments, Debt and Equity Securities [Abstract]
Fair value	266,528	278,302
International securities
Investments, Debt and Equity Securities [Abstract]
Fair value	27,643	29,750
Level 1
Investments, Debt and Equity Securities [Abstract]
Fair value	38,511	83,764
Equity securities, at fair value	1,881	17,361
Total investments, at fair value	40,392	101,125
Level 1 \| United States government obligations and authorities
Investments, Debt and Equity Securities [Abstract]
Fair value	38,511	83,764
Level 1 \| Obligations of states and political subdivisions
Investments, Debt and Equity Securities [Abstract]
Fair value	0	0
Level 1 \| Corporate securities
Investments, Debt and Equity Securities [Abstract]
Fair value	0	0
Level 1 \| International securities
Investments, Debt and Equity Securities [Abstract]
Fair value	0	0
Level 2
Investments, Debt and Equity Securities [Abstract]
Fair value	449,699	442,501
Equity securities, at fair value	1,276	2,678
Total investments, at fair value	450,975	445,179
Level 2 \| United States government obligations and authorities
Investments, Debt and Equity Securities [Abstract]
Fair value	133,264	110,429
Level 2 \| Obligations of states and political subdivisions
Investments, Debt and Equity Securities [Abstract]
Fair value	22,264	24,020
Level 2 \| Corporate securities
Investments, Debt and Equity Securities [Abstract]
Fair value	266,528	278,302
Level 2 \| International securities
Investments, Debt and Equity Securities [Abstract]
Fair value	27,643	29,750
Level 3
Investments, Debt and Equity Securities [Abstract]
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]
Fair value	0	0
Level 3 \| Obligations of states and political subdivisions
Investments, Debt and Equity Securities [Abstract]
Fair value	0	0
Level 3 \| Corporate securities
Investments, Debt and Equity Securities [Abstract]
Fair value	0	0
Level 3 \| International securities
Investments, Debt and Equity Securities [Abstract]
Fair value	$ 0	$ 0