OPERATING SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
REVENUE
Net premiums earned	$ 149,943	$ 146,552	$ 428,807	$ 393,429
Net investment income	14,221	15,954	44,340	47,437
Net realized gains (losses)	5,481	(177)	16,233	14,345
Consolidated revenue	169,645	162,329	489,380	455,211
NET EARNINGS
Net underwriting income	18,530	21,524	55,094	84,561
Net investment income	14,221	15,954	44,340	47,437
Net realized gains (losses)	5,481	(177)	16,233	14,345
General corporate expense and interest on debt	(3,611)	(3,107)	(10,438)	(10,100)
Equity in earnings of unconsolidated investee	1,859	713	8,928	7,215
Earnings before income taxes	36,480	34,907	114,157	143,458
Income tax expense	11,017	10,938	35,908	46,791
Net earnings	25,463	23,969	78,249	96,667
Casualty
REVENUE
Net premiums earned	68,194	60,626	197,409	173,937
NET EARNINGS
Net underwriting income	10,806	22,265	22,409	53,645
Property
REVENUE
Net premiums earned	54,741	59,226	151,581	148,015
NET EARNINGS
Net underwriting income	(310)	(1,813)	11,317	15,653
Surety
REVENUE
Net premiums earned	27,008	26,700	79,817	71,477
NET EARNINGS
Net underwriting income	$ 8,034	$ 1,072	$ 21,368	$ 15,263