OPERATING SEGMENT INFORMATION (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
REVENUE
Net premiums earned	$ 130,826	$ 121,758	$ 246,877	$ 238,022
Net investment income	15,180	16,765	31,483	33,365
Net realized gains (losses)	10,050	4,291	14,522	10,754
Consolidated revenue	156,056	142,814	292,882	282,141
NET EARNINGS
Net underwriting income	45,765	30,801	64,797	43,516
Net investment income	15,180	16,765	31,483	33,365
Net realized gains (losses)	10,050	4,291	14,522	10,754
General corporate expense and interest on debt	(3,476)	(3,054)	(6,993)	(6,283)
Equity in earnings of unconsolidated investee	3,886	3,426	6,502	5,679
Earnings before income taxes	71,405	52,229	110,311	87,031
Income tax expense	24,024	17,235	36,469	27,816
Net earnings	47,381	34,994	73,842	59,215
Casualty
REVENUE
Net premiums earned	58,332	58,640	113,311	118,006
NET EARNINGS
Net underwriting income	26,920	13,594	31,594	14,208
Property
REVENUE
Net premiums earned	47,963	43,644	88,789	81,966
NET EARNINGS
Net underwriting income	9,167	9,334	18,548	17,381
Surety
REVENUE
Net premiums earned	24,531	19,474	44,777	38,050
NET EARNINGS
Net underwriting income	$ 9,678	$ 7,873	$ 14,655	$ 11,927