INVESTMENTS (Gross Unrealized Losses and Related Fair Values for Debt and Equity Securities, Grouped by Duration of Time in Continuous Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair value [Abstract]
Less than 12 months	$ 149,112	$ 219,575
12 months or longer	2,722	3,984
Total fair value	151,834	223,559
Gross unrealized losses [Abstract]
Less than 12 months	2,258	4,152
12 months or longer	188	70
Total gross unrealized losses	2,446	4,222
Debt Securities [Member]
Fair value [Abstract]
Less than 12 months	142,385	214,874
12 months or longer	1,890	3,550
Total fair value	144,275	218,424
Gross unrealized losses [Abstract]
Less than 12 months	1,842	3,899
12 months or longer	18	35
Total gross unrealized losses	1,860	3,934
United States Government Obligations and Authorities [Member]
Fair value [Abstract]
Less than 12 months	33,711	45,255
12 months or longer	106	111
Total fair value	33,817	45,366
Gross unrealized losses [Abstract]
Less than 12 months	535	850
12 months or longer	3	3
Total gross unrealized losses	538	853
Obligations of States and Political Subdivisions [Member]
Fair value [Abstract]
Less than 12 months	37,406	103,724
12 months or longer		1,007
Total fair value	37,406	104,731
Gross unrealized losses [Abstract]
Less than 12 months	511	2,066
12 months or longer		1
Total gross unrealized losses	511	2,067
Corporate [Member]
Fair value [Abstract]
Less than 12 months	65,054	59,970
12 months or longer	1,779	2,427
Total fair value	66,833	62,397
Gross unrealized losses [Abstract]
Less than 12 months	702	864
12 months or longer	15	31
Total gross unrealized losses	717	895
International [Member]
Fair value [Abstract]
Less than 12 months	6,214	5,925
12 months or longer	5	5
Total fair value	6,219	5,930
Gross unrealized losses [Abstract]
Less than 12 months	94	119
Total gross unrealized losses	94	119
Equity Securities [Member]
Fair value [Abstract]
Less than 12 months	6,727	4,701
12 months or longer	832	434
Total fair value	7,559	5,135
Gross unrealized losses [Abstract]
Less than 12 months	416	253
12 months or longer	170	35
Total gross unrealized losses	$ 586	$ 288