OPERATING SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
REVENUE
Segment totals before income taxes	$ 154,553	$ 141,584	$ 298,704	$ 278,864
Net investment income	12,847	14,826	25,733	30,119
Net realized gains (losses)	3,742	(664)	7,426	10,752
Consolidated revenue	171,142	155,746	331,863	319,735
NET EARNINGS
Net underwriting income	25,559	21,623	45,357	36,564
Net investment income	12,847	14,826	25,733	30,119
Net realized gains (losses)	3,742	(664)	7,426	10,752
General corporate expense and interest on debt	(3,205)	(3,340)	(7,103)	(6,827)
Equity in earnings of unconsolidated investee	4,633	4,123	8,132	7,069
Earnings before income taxes	43,576	36,568	79,545	77,677
Income tax expense	13,674	11,820	24,796	24,891
Net earnings	29,902	24,748	54,749	52,786
Casualty
REVENUE
Segment totals before income taxes	78,372	65,705	151,341	129,215
NET EARNINGS
Net underwriting income	14,614	11,051	18,718	11,603
Property
REVENUE
Segment totals before income taxes	49,619	49,848	94,600	96,840
NET EARNINGS
Net underwriting income	2,222	(290)	13,146	11,627
Surety
REVENUE
Segment totals before income taxes	26,562	26,031	52,763	52,809
NET EARNINGS
Net underwriting income	$ 8,723	$ 10,862	$ 13,493	$ 13,334