OPERATING SEGMENT INFORMATION (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenue by major product
Net premiums earned	$ 163,702	$ 149,943	$ 462,406	$ 428,807
Casualty
Revenue by major product
Net premiums earned	83,966	68,194	235,307	197,409
Casualty | General liability
Revenue by major product
Net premiums earned	20,342	21,556	61,139	63,449
Casualty | Commercial and personal umbrella
Revenue by major product
Net premiums earned	22,247	17,430	61,803	50,337
Casualty | Commercial transportation
Revenue by major product
Net premiums earned	13,463	8,583	35,594	25,252
Casualty | P&C package business
Revenue by major product
Net premiums earned	7,643	7,479	22,671	21,334
Casualty | Executive products
Revenue by major product
Net premiums earned	4,550	3,914	13,175	11,666
Casualty | Professional services
Revenue by major product
Net premiums earned	11,021	7,386	30,092	19,704
Casualty | Medical professional liability
Revenue by major product
Net premiums earned	2,674		5,136
Casualty | Other
Revenue by major product
Net premiums earned	2,026	1,846	5,697	5,667
Property
Revenue by major product
Net premiums earned	52,705	54,741	147,305	151,581
Property | Commercial property
Revenue by major product
Net premiums earned	18,938	18,640	57,813	55,285
Property | Marine
Revenue by major product
Net premiums earned	14,242	14,026	43,898	44,591
Property | Crop reinsurance
Revenue by major product
Net premiums earned	11,846	9,876	19,501	15,992
Property | Property reinsurance
Revenue by major product
Net premiums earned	2,848	6,826	12,503	20,193
Property | Other property
Revenue by major product
Net premiums earned	4,831	5,373	13,590	15,520
Surety
Revenue by major product
Net premiums earned	27,031	27,008	79,794	79,817
Surety | Miscellaneous
Revenue by major product
Net premiums earned	9,590	10,026	28,559	29,600
Surety | Contract
Revenue by major product
Net premiums earned	7,025	6,835	20,137	19,507
Surety | Commercial
Revenue by major product
Net premiums earned	5,857	5,574	17,285	16,536
Surety | Oil and Gas
Revenue by major product
Net premiums earned	$ 4,559	$ 4,573	$ 13,813	$ 14,174