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, 2019	Dec. 31, 2018
Gross unrealized losses [Abstract]
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 194	$ 874
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	8
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	3,363	3,203
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	93	157
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	3,557	4,077
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	93	165
Debt Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	40,697	202,770
Debt Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	346	3,547
Debt Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	103,844	95,626
Debt Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,574	3,281
Debt Securities, Unrealized Loss Position, Fair Value	144,541	298,396
Debt Securities, Unrealized Loss Position, Accumulated Loss	1,920	6,828
Debt Securities
Fair value [Abstract]
Less than 12 months	40,503	201,896
12 months or longer	100,481	92,423
Total	140,984	294,319
Gross unrealized losses [Abstract]
Less than 12 months	346	3,539
12 months or longer	1,481	3,124
Total	1,827	6,663
United States Government Obligations and Authorities
Fair value [Abstract]
Less than 12 months	10,279	22,673
12 months or longer	32,169	29,727
Total	42,448	52,400
Gross unrealized losses [Abstract]
Less than 12 months	8	246
12 months or longer	517	905
Total	525	1,151
Obligations of States and Political Subdivisions
Fair value [Abstract]
Less than 12 months	790	3,254
12 months or longer	5,339	4,786
Total	6,129	8,040
Gross unrealized losses [Abstract]
Less than 12 months	21	18
12 months or longer	50	112
Total	71	130
Corporate
Fair value [Abstract]
Less than 12 months	26,723	160,361
12 months or longer	57,096	53,232
Total	83,819	213,593
Gross unrealized losses [Abstract]
Less than 12 months	311	3,058
12 months or longer	841	1,913
Total	1,152	4,971
International
Fair value [Abstract]
Less than 12 months	2,711	15,608
12 months or longer	5,877	4,678
Total	8,588	20,286
Gross unrealized losses [Abstract]
Less than 12 months	6	217
12 months or longer	73	194
Total	79	411
United States Government Obligations and Authorities
Gross unrealized losses [Abstract]
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	114	229
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	1
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	3,161	3,113
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	91	157
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	3,275	3,342
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	91	158
Corporate
Gross unrealized losses [Abstract]
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	80	591
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	6
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	173	90
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2	0
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	253	681
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	2	6
International
Gross unrealized losses [Abstract]
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	0	54
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	1
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	29	0
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	29	54
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	$ 0	$ 1