INVESTMENTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	$ 1,274,393	$ 1,203,978
Gross unrealized gains	107,244	128,038
Gross unrealized losses	14,369	7,481
Estimated fair value	1,367,268	1,324,535
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	243,068	74,394
Less than twelve months, Unrealized losses	7,792	2,142
Twelve months or longer, Fair value	73,043	152,526
Twelve months or longer, Unrealized losses	6,577	5,339
Total, Fair value	316,111	226,920
Total, Unrealized losses	14,369	7,481
Amortized cost
Due in one year or less	60,081
Due after one year through five years	146,288
Due after five years through ten years	315,753
Due after ten years	465,651
Securities not due at a single maturity date	142,444
Totals	1,130,217	1,080,006
Estimated fair value
Due in one year or less	60,344
Due after one year through five years	153,326
Due after five years through ten years	320,416
Due after ten years	488,547
Securities not due at a single maturity date	138,392
Totals	1,161,025	1,127,499
Realized Investment Gains (Losses) [Abstract]
'Other-than-temporary' impairments	(1,481)	(878)	$ (63)
Net realized investment gains	6,153	4,349	8,997
Investment Income, Net [Abstract]
Interest on fixed maturity securities	42,261	41,932	40,062
Dividends on equity securities	5,617	6,007	4,619
Income on reverse repurchase agreements	117	0	0
Interest on short-term investments	2	0	27
Return on long-term investments	(461)	297	22
Total investment income	47,536	48,236	44,730
Securities litigation income	32	107	219
Investment expenses	(1,986)	(1,878)	(1,927)
Net investment income (loss)	45,582	46,465	43,022
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax [Abstract]
Deferred income tax expense (benefit)	(9,689)	16,146	(11,539)
Net changes in unrealized holding gains (losses) net of tax	(17,993)	29,986	(21,430)
Debt Securities [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	1,130,217	1,080,006
Gross unrealized gains	42,885	54,148
Gross unrealized losses	12,077	6,655
Estimated fair value	1,161,025	1,127,499
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	214,736	65,655
Less than twelve months, Unrealized losses	5,661	1,633
Twelve months or longer, Fair value	71,072	150,623
Twelve months or longer, Unrealized losses	6,416	5,022
Total, Fair value	285,808	216,278
Total, Unrealized losses	12,077	6,655
Realized Investment Gains (Losses) [Abstract]
Available-for-sale, Gross realized investment gains	725	979	1,226
Available-for-sale, Gross realized investment losses	(251)	(92)	(725)
'Other-than-temporary' impairments	0	(1)	0
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax [Abstract]
Net changes in unrealized holding gains (losses) before tax	(16,685)	29,081	(60,540)
Deferred income tax expense (benefit)	(5,840)	10,179	(21,189)
Net changes in unrealized holding gains (losses) net of tax	(10,845)	18,902	(39,351)
US Treasury Securities [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	12,566	9,574
Gross unrealized gains	23	129
Gross unrealized losses	0	0
Estimated fair value	12,589	9,703
US Government-sponsored Enterprises Debt Securities [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	202,486	215,425
Gross unrealized gains	1,817	2,313
Gross unrealized losses	1,637	2,122
Estimated fair value	202,666	215,616
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	78,800	24,473
Less than twelve months, Unrealized losses	1,228	94
Twelve months or longer, Fair value	34,079	97,446
Twelve months or longer, Unrealized losses	409	2,028
Total, Fair value	112,879	121,919
Total, Unrealized losses	1,637	2,122
US States and Political Subdivisions Debt Securities [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	319,940	299,258
Gross unrealized gains	24,419	26,840
Gross unrealized losses	0	40
Estimated fair value	344,359	326,058
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value		0
Less than twelve months, Unrealized losses		0
Twelve months or longer, Fair value		3,757
Twelve months or longer, Unrealized losses		40
Total, Fair value		3,757
Total, Unrealized losses		40
Commercial Mortgage Backed Securities [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	44,433	42,996
Gross unrealized gains	1,692	3,766
Gross unrealized losses	17	0
Estimated fair value	46,108	46,762
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	6,807	1,102
Less than twelve months, Unrealized losses	17	0
Twelve months or longer, Fair value	0	0
Twelve months or longer, Unrealized losses	0	0
Total, Fair value	6,807	1,102
Total, Unrealized losses	17	0
Residential Mortgage Backed Securities [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	94,279	100,296
Gross unrealized gains	1,059	1,402
Gross unrealized losses	6,795	3,745
Estimated fair value	88,543	97,953
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	22,028	21,451
Less than twelve months, Unrealized losses	1,694	1,252
Twelve months or longer, Fair value	22,781	21,163
Twelve months or longer, Unrealized losses	5,101	2,493
Total, Fair value	44,809	42,614
Total, Unrealized losses	6,795	3,745
Collateralized Debt Obligations [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	17,000	14,798
Gross unrealized gains	883	1,213
Gross unrealized losses	39	6
Estimated fair value	17,844	16,005
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	6,013	1,889
Less than twelve months, Unrealized losses	39	6
Twelve months or longer, Fair value	0	0
Twelve months or longer, Unrealized losses	0	0
Total, Fair value	6,013	1,889
Total, Unrealized losses	39	6
Corporate Debt Securities [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	439,513	397,659
Gross unrealized gains	12,992	18,485
Gross unrealized losses	3,589	742
Estimated fair value	448,916	415,402
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	101,088	16,740
Less than twelve months, Unrealized losses	2,683	281
Twelve months or longer, Fair value	14,212	28,257
Twelve months or longer, Unrealized losses	906	461
Total, Fair value	115,300	44,997
Total, Unrealized losses	3,589	742
Equity Securities [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	144,176	123,972
Gross unrealized gains	64,359	73,890
Gross unrealized losses	2,292	826
Estimated fair value	206,243	197,036
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	28,332	8,739
Less than twelve months, Unrealized losses	2,131	509
Twelve months or longer, Fair value	1,971	1,903
Twelve months or longer, Unrealized losses	161	317
Total, Fair value	30,303	10,642
Total, Unrealized losses	2,292	826
Realized Investment Gains (Losses) [Abstract]
Available-for-sale, Gross realized investment gains	12,741	8,913	9,458
Available-for-sale, Gross realized investment losses	(4,110)	(1,727)	(899)
'Other-than-temporary' impairments	(1,481)	(877)	(63)
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax [Abstract]
Net changes in unrealized holding gains (losses) before tax	(10,997)	17,051	27,571
Deferred income tax expense (benefit)	(3,849)	5,967	9,650
Net changes in unrealized holding gains (losses) net of tax	(7,148)	11,084	17,921
Common stocks Financial services [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	24,557	22,586
Gross unrealized gains	9,731	11,835
Gross unrealized losses	333	42
Estimated fair value	33,955	34,379
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	6,387	1,162
Less than twelve months, Unrealized losses	333	9
Twelve months or longer, Fair value	0	187
Twelve months or longer, Unrealized losses	0	33
Total, Fair value	6,387	1,349
Total, Unrealized losses	333	42
Common stocks Information technology [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	19,427	15,755
Gross unrealized gains	8,807	11,110
Gross unrealized losses	132	0
Estimated fair value	28,102	26,865
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	1,316
Less than twelve months, Unrealized losses	132
Twelve months or longer, Fair value	0
Twelve months or longer, Unrealized losses	0
Total, Fair value	1,316
Total, Unrealized losses	132
Common stocks Healthcare [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	15,599	14,673
Gross unrealized gains	10,359	12,179
Gross unrealized losses	64	0
Estimated fair value	25,894	26,852
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	3,199
Less than twelve months, Unrealized losses	64
Twelve months or longer, Fair value	0
Twelve months or longer, Unrealized losses	0
Total, Fair value	3,199
Total, Unrealized losses	64
Common stocks Consumer staples [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	11,136	10,584
Gross unrealized gains	7,090	6,112
Gross unrealized losses	26	2
Estimated fair value	18,200	16,694
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	1,244	1,051
Less than twelve months, Unrealized losses	26	2
Twelve months or longer, Fair value	0	0
Twelve months or longer, Unrealized losses	0	0
Total, Fair value	1,244	1,051
Total, Unrealized losses	26	2
Common stocks Consumer discretionary [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	10,270	11,304
Gross unrealized gains	8,658	11,420
Gross unrealized losses	5	33
Estimated fair value	18,923	22,691
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	176	822
Less than twelve months, Unrealized losses	5	33
Twelve months or longer, Fair value	0	0
Twelve months or longer, Unrealized losses	0	0
Total, Fair value	176	822
Total, Unrealized losses	5	33
Common stocks Energy [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	16,384	15,837
Gross unrealized gains	5,972	7,458
Gross unrealized losses	1,288	432
Estimated fair value	21,068	22,863
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	8,233	4,298
Less than twelve months, Unrealized losses	1,272	432
Twelve months or longer, Fair value	116	0
Twelve months or longer, Unrealized losses	16	0
Total, Fair value	8,349	4,298
Total, Unrealized losses	1,288	432
Common stocks Industrials [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	11,525	9,658
Gross unrealized gains	8,902	8,596
Gross unrealized losses	11	33
Estimated fair value	20,416	18,221
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	1,263	1,406
Less than twelve months, Unrealized losses	11	33
Twelve months or longer, Fair value	0	0
Twelve months or longer, Unrealized losses	0	0
Total, Fair value	1,263	1,406
Total, Unrealized losses	11	33
Common stocks Other [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	17,246	11,493
Gross unrealized gains	3,672	4,563
Gross unrealized losses	235	0
Estimated fair value	20,683	16,056
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	4,064
Less than twelve months, Unrealized losses	235
Twelve months or longer, Fair value	0
Twelve months or longer, Unrealized losses	0
Total, Fair value	4,064
Total, Unrealized losses	235
Nonredeemable Preferred Stock [Member]
Amortized cost and estimated fair value of available-for-sale securities [Abstract]
Amortized cost	18,032	12,082
Gross unrealized gains	1,168	617
Gross unrealized losses	198	284
Estimated fair value	19,002	12,415
Available for sale securities continuous unrealized loss position [Abstract]
Less than twelve months, Fair value	2,450	0
Less than twelve months, Unrealized losses	53	0
Twelve months or longer, Fair value	1,855	1,716
Twelve months or longer, Unrealized losses	145	284
Total, Fair value	4,305	1,716
Total, Unrealized losses	198	284
Other Long-term Investments [Member]
Realized Investment Gains (Losses) [Abstract]
Other long-term investments, net	$ (1,471)	$ (2,846)	$ 0