FAIR VALUE (Financial Instruments Measured at Fair Value) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Debt securities	$ 375,970	$ 374,756
Equity securities	44,003	29,375
Total investments	419,973	404,131
United States Government Obligations and Authorities [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	75,395	62,205
Total investments	75,395	62,205
Obligations of States and Political Subdivisions [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	86,974	151,183
Total investments	86,974	151,183
Corporate [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	198,047	149,505
Total investments	198,047	149,505
International [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	15,554	11,863
Total investments	15,554	11,863
Level 1 [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	37,790	36,560
Equity securities	44,003	28,960
Total investments	81,793	65,520
Level 1 [Member] | United States Government Obligations and Authorities [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	37,790	36,560
Level 2 [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	338,180	338,196
Equity securities		415
Total investments	338,180	338,611
Level 2 [Member] | United States Government Obligations and Authorities [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	37,605	25,645
Level 2 [Member] | Obligations of States and Political Subdivisions [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	86,974	151,183
Level 2 [Member] | Corporate [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	198,047	149,505
Level 2 [Member] | International [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities	$ 15,554	$ 11,863