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	Jun. 30, 2019	Dec. 31, 2018
Fair Value [Abstract]
Less than 12 months	$ 20	$ 874
12 months or longer	2,934	3,203
Total	2,954	4,077
Gross unrealized loss position [Abstract]
Less than 12 months	0	8
12 Months or longer	68	157
Total	68	165
Total Investments, excluding equity securities, less than 12 months, Fair Value	17,813	202,770
Total Investments, excluding equity securities, Less than 12 Months, Gross Unrealized Losses	99	3,547
Total Investments, excluding equity securities, 12 months or longer, Fair Value	43,118	95,626
Total Investments, excluding equity securities, 12 months or longer, Gross Unrealized Losses	289	3,281
Total Investments, excluding equity securities, Total Fair Value	60,931	298,396
Total Investments, excluding equity securities, Total Gross Unrealized Losses	388	6,828
United States Government Obligations and Authorities
Fair value [Abstract]
Less than 12 months	3,088	22,673
12 months or longer	21,210	29,727
Total	24,298	52,400
Gross unrealized losses [Abstract]
Less than 12 months	2	246
12 months or longer	147	905
Total	149	1,151
Fair Value [Abstract]
Less than 12 months	0	229
12 months or longer	2,894	3,113
Total	2,894	3,342
Gross unrealized loss position [Abstract]
Less than 12 months	0	1
12 Months or longer	68	157
Total	68	158
Obligations of States and Political Subdivisions
Fair value [Abstract]
Less than 12 months	0	3,254
12 months or longer	2,606	4,786
Total	2,606	8,040
Gross unrealized losses [Abstract]
Less than 12 months	0	18
12 months or longer	6	112
Total	6	130
Corporate
Fair value [Abstract]
Less than 12 months	11,678	160,361
12 months or longer	15,689	53,232
Total	27,367	213,593
Gross unrealized losses [Abstract]
Less than 12 months	87	3,058
12 months or longer	67	1,913
Total	154	4,971
Fair Value [Abstract]
Less than 12 months	20	591
12 months or longer	0	90
Total	20	681
Gross unrealized loss position [Abstract]
Less than 12 months	0	6
12 Months or longer	0	0
Total	0	6
International
Fair value [Abstract]
Less than 12 months	3,027	15,608
12 months or longer	679	4,678
Total	3,706	20,286
Gross unrealized losses [Abstract]
Less than 12 months	10	217
12 months or longer	1	194
Total	11	411
Fair Value [Abstract]
Less than 12 months	0	54
12 months or longer	40	0
Total	40	54
Gross unrealized loss position [Abstract]
Less than 12 months	0	1
12 Months or longer	0	0
Total	0	1
Debt Securities
Fair value [Abstract]
Less than 12 months	17,793	201,896
12 months or longer	40,184	92,423
Total	57,977	294,319
Gross unrealized losses [Abstract]
Less than 12 months	99	3,539
12 months or longer	221	3,124
Total	$ 320	$ 6,663