UNAUDITED INTERIM FINANCIAL INFORMATION (Details) - 10K (USD $) In Thousands, except Per Share data, 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
UNAUDITED INTERIM FINANCIAL INFORMATION
Net premiums earned	$ 179,892	$ 177,747	$ 168,604	$ 161,132	$ 168,396	$ 163,702	$ 154,553	$ 144,151	$ 687,375	$ 630,802	$ 576,571
Net investment income	13,844	14,200	13,982	13,582	13,432	13,598	12,847	12,886	55,608	52,763	58,831
Net realized investment gains (losses)	9,542	5,708	10,431	6,501	3,611	10,999	3,742	3,684	32,182	22,036	25,372
Earnings before income taxes	46,479	48,594	52,423	41,991	40,812	55,309	43,576	35,969	189,487	175,666	142,732
Net earnings	$ 37,497	$ 33,254	$ 35,725	$ 28,969	$ 33,859	$ 37,647	$ 29,902	$ 24,847	$ 135,445	$ 126,255	$ 103,346
Basic earnings per share (in dollars per share)	$ 0.87	$ 0.77	$ 0.83	$ 0.67	$ 0.79	$ 0.88	$ 0.70	$ 0.58	$ 3.15	$ 2.95	$ 2.44
Diluted earnings per share (in dollars per share)	$ 0.85	$ 0.76	$ 0.82	$ 0.66	$ 0.77	$ 0.86	$ 0.69	$ 0.57	$ 3.09	$ 2.90	$ 2.39