OPERATING SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
REVENUE
Net premiums earned	$ 137,280	$ 116,051
Net investment income	15,293	16,303
Net realized gains (losses)	11,416	4,472
Consolidated revenue	163,989	136,826
NET EARNINGS
Net underwriting income	14,941	20,947
Net investment income	15,293	16,303
Net realized gains (losses)	11,416	4,472
General corporate expense and interest on debt	(3,487)	(3,517)
Equity in earnings of unconsolidated investee	2,946	2,616
Earnings before income taxes	41,109	40,821
Income tax expense	13,071	13,115
Net earnings	28,038	27,706
Casualty
REVENUE
Net premiums earned	63,510	54,979
NET EARNINGS
Net underwriting income	552	5,537
Property
REVENUE
Net premiums earned	46,992	40,826
NET EARNINGS
Net underwriting income	11,917	10,033
Surety
REVENUE
Net premiums earned	26,778	20,246
NET EARNINGS
Net underwriting income	$ 2,472	$ 5,377