FAIR VALUE (Financial Instruments Measured at Fair Value) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	$ 422,359	$ 374,756
Equity securities, available-for-sale	15,575	29,375
Total investments	437,934	404,131
United States Government Obligations and Authorities [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	116,210	62,205
Total investments	116,210	62,205
Obligations of States and Political Subdivisions [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	72,999	151,183
Total investments	72,999	151,183
Corporate [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	219,401	149,505
Total investments	219,401	149,505
International [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	13,749	11,863
Total investments	13,749	11,863
Level 1 [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	71,956	36,560
Equity securities, available-for-sale	15,575	28,960
Total investments	87,531	65,520
Level 1 [Member] | United States Government Obligations and Authorities [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	69,855	36,560
Level 1 [Member] | Obligations of States and Political Subdivisions [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	1,632
Level 1 [Member] | Corporate [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	469
Level 2 [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	350,403	338,196
Equity securities, available-for-sale		415
Total investments	350,403	338,611
Level 2 [Member] | United States Government Obligations and Authorities [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	46,355	25,645
Level 2 [Member] | Obligations of States and Political Subdivisions [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	71,367	151,183
Level 2 [Member] | Corporate [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	218,932	149,505
Level 2 [Member] | International [Member]
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale	$ 13,749	$ 11,863