FAIR VALUE - (Financial Instruments Measured at Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	$ 423,238	$ 374,756
Equity securities, available-for-sale, at fair value	15,434	29,375
Total investments	438,672	404,131
United States Government Obligations and Authorities [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	98,137	62,205
Total investments	98,137	62,205
Held-to-maturity securities, fair Value	4,063	4,067
Obligations of States and Political Subdivisions [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	66,266	151,183
Total investments	66,266	151,183
Corporate [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	240,919	149,505
Total investments	240,919	149,505
Held-to-maturity securities, fair Value	1,144	1,335
International [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	17,916	11,863
Total investments	17,916	11,863
Held-to-maturity securities, fair Value	67	71
Level 1 [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	51,219	36,560
Equity securities, available-for-sale, at fair value	15,434	28,960
Total investments	66,653	65,520
Held-to-maturity securities, fair Value	4,000	4,000
Level 1 [Member] | United States Government Obligations and Authorities [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	51,219	36,560
Level 2 [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	372,019	338,196
Equity securities, available-for-sale, at fair value	0	415
Total investments	372,019	338,611
Held-to-maturity securities, fair Value	1,300	1,600
Level 2 [Member] | United States Government Obligations and Authorities [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	46,918	25,645
Level 2 [Member] | Obligations of States and Political Subdivisions [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	66,266	151,183
Level 2 [Member] | Corporate [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	240,919	149,505
Level 2 [Member] | International [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available for sale, at fair value	$ 17,916	$ 11,863