OPERATING SEGMENT INFORMATION (Details 2) (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 by major product
Net premiums earned	$ 154,553	$ 141,584	$ 298,704	$ 278,864
Casualty
Revenue by major product
Net premiums earned	78,372	65,705	151,341	129,215
Casualty | General liability
Revenue by major product
Net premiums earned	20,020	21,136	40,797	41,893
Casualty | Commercial and personal umbrella
Revenue by major product
Net premiums earned	20,606	16,747	39,556	32,907
Casualty | Commercial transportation
Revenue by major product
Net premiums earned	12,197	8,362	22,131	16,669
Casualty | P&C package business
Revenue by major product
Net premiums earned	7,607	6,956	15,028	13,855
Casualty | Executive products
Revenue by major product
Net premiums earned	4,279	3,942	8,625	7,752
Casualty | Professional services
Revenue by major product
Net premiums earned	10,062	6,650	19,071	12,318
Casualty | Medical professional liability
Revenue by major product
Net premiums earned	1,712		2,462
Casualty | Other
Revenue by major product
Net premiums earned	1,889	1,912	3,671	3,821
Property
Revenue by major product
Net premiums earned	49,619	49,848	94,600	96,840
Property | Commercial property
Revenue by major product
Net premiums earned	19,259	18,093	38,875	36,645
Property | Marine
Revenue by major product
Net premiums earned	15,042	15,351	29,656	30,565
Property | Crop reinsurance
Revenue by major product
Net premiums earned	6,388	5,066	7,655	6,116
Property | Property reinsurance
Revenue by major product
Net premiums earned	4,383	5,980	9,655	13,367
Property | Other property
Revenue by major product
Net premiums earned	4,547	5,358	8,759	10,147
Surety
Revenue by major product
Net premiums earned	26,562	26,031	52,763	52,809
Surety | Miscellaneous
Revenue by major product
Net premiums earned	9,488	9,788	18,969	19,574
Surety | Contract
Revenue by major product
Net premiums earned	6,653	6,122	13,112	12,672
Surety | Commercial
Revenue by major product
Net premiums earned	5,717	5,557	11,428	10,962
Surety | Oil and gas
Revenue by major product
Net premiums earned	$ 4,704	$ 4,564	$ 9,254	$ 9,601