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	Sep. 30, 2019	Dec. 31, 2018
Fair Value [Abstract]
Less than 12 Months	$ 120	$ 874
12 Months or Longer, Fair Value	2,306	3,203
Total	2,426	4,077
Gross unrealized loss position [Abstract]
Less than 12 Months	0	8
12 Months or Longer, Accumulated Loss	62	157
Total	62	165
Total Investments, excluding equity securities, less than 12 months, Fair Value	33,772	202,770
Total Investments, excluding equity securities, Less than 12 Months, Gross Unrealized Losses	169	3,547
Total Investments, excluding equity securities, 12 months or longer, Fair Value	14,844	95,626
Total Investments, excluding equity securities, 12 months or longer, Gross Unrealized Losses	161	3,281
Total Investments, excluding equity securities, Total Fair Value	48,616	298,396
Total Investments, excluding equity securities, Total Gross Unrealized Losses	330	6,828
United States Government Obligations and Authorities
Fair value [Abstract]
Less than 12 months	20,948	22,673
12 Months or Longer	6,238	29,727
Total	27,186	52,400
Gross unrealized losses [Abstract]
Less than 12 months	115	246
12 Months or Longer	31	905
Total	146	1,151
Fair Value [Abstract]
Less than 12 Months	100	229
12 Months or Longer, Fair Value	2,306	3,113
Total	2,406	3,342
Gross unrealized loss position [Abstract]
Less than 12 Months	0	1
12 Months or Longer, Accumulated Loss	62	157
Total	62	158
Obligations of States and Political Subdivisions
Fair value [Abstract]
Less than 12 months	0	3,254
12 Months or Longer	0	4,786
Total	0	8,040
Gross unrealized losses [Abstract]
Less than 12 months	0	18
12 Months or Longer	0	112
Total	0	130
Corporate
Fair value [Abstract]
Less than 12 months	10,502	160,361
12 Months or Longer	5,277	53,232
Total	15,779	213,593
Gross unrealized losses [Abstract]
Less than 12 months	36	3,058
12 Months or Longer	65	1,913
Total	101	4,971
Fair Value [Abstract]
Less than 12 Months	20	591
12 Months or Longer, Fair Value	0	90
Total	20	681
Gross unrealized loss position [Abstract]
Less than 12 Months	0	6
12 Months or Longer, Accumulated Loss	0	0
Total	0	6
International
Fair value [Abstract]
Less than 12 months	2,202	15,608
12 Months or Longer	1,023	4,678
Total	3,225	20,286
Gross unrealized losses [Abstract]
Less than 12 months	18	217
12 Months or Longer	3	194
Total	21	411
Fair Value [Abstract]
Less than 12 Months	0	54
12 Months or Longer, Fair Value	0	0
Total	0	54
Gross unrealized loss position [Abstract]
Less than 12 Months	0	1
12 Months or Longer, Accumulated Loss	0	0
Total	0	1
Debt Securities
Fair value [Abstract]
Less than 12 months	33,652	201,896
12 Months or Longer	12,538	92,423
Total	46,190	294,319
Gross unrealized losses [Abstract]
Less than 12 months	169	3,539
12 Months or Longer	99	3,124
Total	$ 268	$ 6,663