OPERATING SEGMENT INFORMATION (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenue by major product
Net premiums earned	$ 168,604	$ 154,553	$ 329,736	$ 298,704
Casualty
Revenue by major product
Net premiums earned	94,360	78,372	185,337	151,341
Casualty | Commercial and personal umbrella
Revenue by major product
Net premiums earned	25,024	20,606	49,780	39,556
Casualty | General liability
Revenue by major product
Net premiums earned	20,523	20,020	40,455	40,797
Casualty | Commercial transportation
Revenue by major product
Net premiums earned	15,005	12,197	29,516	22,131
Casualty | Professional services
Revenue by major product
Net premiums earned	13,839	10,062	26,700	19,071
Casualty | P&C package business
Revenue by major product
Net premiums earned	8,495	7,607	16,778	15,028
Casualty | Executive products
Revenue by major product
Net premiums earned	4,721	4,651	9,405	9,367
Casualty | Medical professional liability
Revenue by major product
Net premiums earned	3,724	1,712	7,424	2,462
Casualty | Other casualty
Revenue by major product
Net premiums earned	3,029	1,517	5,279	2,929
Property
Revenue by major product
Net premiums earned	48,791	49,619	92,109	94,600
Property | Commercial property
Revenue by major product
Net premiums earned	20,054	19,259	40,487	38,875
Property | Marine
Revenue by major product
Net premiums earned	12,962	15,042	25,163	29,656
Property | Property reinsurance
Revenue by major product
Net premiums earned	3,387	4,383	6,748	9,655
Property | Crop reinsurance
Revenue by major product
Net premiums earned	5,683	6,388	6,869	7,655
Property | Other property
Revenue by major product
Net premiums earned	6,705	4,574	12,842	8,759
Surety
Revenue by major product
Net premiums earned	25,453	26,562	52,290	52,763
Surety | Miscellaneous
Revenue by major product
Net premiums earned	9,598	9,488	19,080	18,969
Surety | Contract
Revenue by major product
Net premiums earned	6,256	6,653	13,017	13,112
Surety | Commercial
Revenue by major product
Net premiums earned	6,313	5,717	12,447	11,428
Surety | Oil and Gas
Revenue by major product
Net premiums earned	$ 3,286	$ 4,704	$ 7,746	$ 9,254