SEGMENT INFORMATION (Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net premiums earned									$ 828,330	$ 754,846	$ 694,994
Investment income, net of investment expenses									104,609	112,799	111,905
Net realized investment gains									7,270	8,695	5,453
Other income									1,685	702	891
Total revenues	250,452	235,865	232,673	222,904	228,994	223,024	219,719	205,305	941,894	877,042	813,243
Benefits, losses and expenses									865,431	775,140	767,169
Income before income taxes	50,355	(2,845)	13,056	15,897	37,339	14,395	20,318	29,850	76,463	101,902	46,074
Income tax expense									17,326	25,762	5,862
Net income	34,796	325	10,685	13,331	26,526	11,725	15,496	22,393	59,137	76,140	40,212
Total assets	3,856,689				3,720,672				3,856,689	3,720,672	3,694,653
Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Total revenues									816,263	746,872	673,282
Income before income taxes									66,025	88,719	36,081
Income tax expense									13,649	21,263	2,569
Net income									52,376	67,456	33,512
Total assets	2,127,623				1,995,069				2,127,623	1,995,069	1,905,315
Life Insurance [Member]
Segment Reporting Information [Line Items]
Total revenues									125,631	130,170	139,961
Income before income taxes									10,438	13,183	9,993
Income tax expense									3,677	4,499	3,293
Net income									6,761	8,684	6,700
Total assets	1,729,066				1,725,603				1,729,066	1,725,603	1,789,338
Operating Segments [Member] | Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Net premiums earned									766,939	694,192	629,411
Investment income, net of investment expenses									44,219	46,279	40,305
Net realized investment gains									4,177	6,260	3,896
Other income									910	88	316
Total revenues									816,245	746,819	673,928
Benefits, losses and expenses									750,768	658,645	637,648
Total net income before eliminations									65,477	88,174	36,280
Total assets	2,360,764				2,218,464				2,360,764	2,218,464	2,149,356
Operating Segments [Member] | Life Insurance [Member]
Segment Reporting Information [Line Items]
Net premiums earned									61,921	61,146	66,031
Investment income, net of investment expenses									60,373	66,467	70,026
Net realized investment gains									3,093	2,434	3,777
Other income									774	614	575
Total revenues									126,161	130,661	140,409
Benefits, losses and expenses									115,361	117,159	130,135
Total net income before eliminations									10,800	13,502	10,274
Intersegment Elimination [Member] | Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Total revenues									18	53	(646)
Intersegment eliminations									548	545	(199)
Total assets	(233,141)				(223,395)				(233,141)	(223,395)	(244,041)
Intersegment Elimination [Member] | Life Insurance [Member]
Segment Reporting Information [Line Items]
Total revenues									(530)	(491)	(448)
Intersegment eliminations									$ (362)	$ (319)	$ (281)