OPERATING SEGMENT INFORMATION (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenue by major product
Net premiums earned	$ 149,943	$ 146,552	$ 428,807	$ 393,429
Casualty
Revenue by major product
Net premiums earned	68,194	60,626	197,409	173,937
Casualty | General liability
Revenue by major product
Net premiums earned	21,556	20,693	63,449	63,817
Casualty | Commercial and personal umbrella
Revenue by major product
Net premiums earned	17,430	15,825	50,337	47,110
Casualty | Commercial transportation
Revenue by major product
Net premiums earned	8,583	8,326	25,252	25,843
Casualty | P&C package business
Revenue by major product
Net premiums earned	7,479	6,126	21,334	10,235
Casualty | Executive products
Revenue by major product
Net premiums earned	3,914	3,716	11,666	10,901
Casualty | Professional services
Revenue by major product
Net premiums earned	7,386	3,655	19,704	8,416
Casualty | Specialty programs
Revenue by major product
Net premiums earned	540	948	1,878	3,377
Casualty | Other
Revenue by major product
Net premiums earned	1,306	1,337	3,789	4,238
Property
Revenue by major product
Net premiums earned	54,741	59,226	151,581	148,015
Property | Commercial property
Revenue by major product
Net premiums earned	18,640	20,295	55,285	60,894
Property | Marine
Revenue by major product
Net premiums earned	14,026	13,544	44,591	38,865
Property | Crop reinsurance
Revenue by major product
Net premiums earned	9,876	14,873	15,992	22,207
Property | Property reinsurance
Revenue by major product
Net premiums earned	6,826	6,087	20,193	14,456
Property | Other property
Revenue by major product
Net premiums earned	5,373	4,427	15,520	11,593
Surety
Revenue by major product
Net premiums earned	27,008	26,700	79,817	71,477
Surety | Miscellaneous
Revenue by major product
Net premiums earned	10,026	9,923	29,600	24,947
Surety | Contract
Revenue by major product
Net premiums earned	6,835	6,901	19,507	17,274
Surety | Commercial
Revenue by major product
Net premiums earned	5,574	5,387	16,536	15,770
Surety | Oil and gas
Revenue by major product
Net premiums earned	$ 4,573	$ 4,489	$ 14,174	$ 13,486