OPERATING SEGMENT INFORMATION Major Products (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenue by major product
Net premiums earned	$ 177,747	$ 163,702	$ 507,483	$ 462,406
Casualty segment
Revenue by major product
Net premiums earned	96,181	83,966	281,518	235,307
Casualty segment | Commercial and personal umbrella
Revenue by major product
Net premiums earned	25,256	22,247	75,036	61,803
Casualty segment | General liability
Revenue by major product
Net premiums earned	20,095	20,342	60,550	61,139
Casualty segment | Commercial transportation
Revenue by major product
Net premiums earned	14,677	13,463	44,193	35,594
Casualty segment | P&C package business
Revenue by major product
Net premiums earned	8,969	7,643	25,747	22,671
Casualty segment | Executive products
Revenue by major product
Net premiums earned	4,760	4,933	14,165	14,300
Casualty segment | Professional services
Revenue by major product
Net premiums earned	15,227	11,021	41,927	30,092
Casualty segment | Medical professional liability
Revenue by major product
Net premiums earned	3,546	2,674	10,970	5,136
Casualty segment | Other casualty
Revenue by major product
Net premiums earned	3,651	1,643	8,930	4,572
Property segment
Revenue by major product
Net premiums earned	54,143	52,705	146,252	147,305
Property segment | Commercial products
Revenue by major product
Net premiums earned	20,188	18,938	60,675	57,813
Property segment | Marine
Revenue by major product
Net premiums earned	12,115	14,242	37,278	43,898
Property segment | Crop reinsurance business
Revenue by major product
Net premiums earned	11,802	11,846	18,671	19,501
Property segment | Property reinsurance
Revenue by major product
Net premiums earned	2,997	2,848	9,745	12,503
Property segment | Other property
Revenue by major product
Net premiums earned	7,041	4,831	19,883	13,590
Surety segment
Revenue by major product
Net premiums earned	27,423	27,031	79,713	79,794
Surety segment | Miscellaneous
Revenue by major product
Net premiums earned	9,868	9,590	28,948	28,559
Surety segment | Contract
Revenue by major product
Net premiums earned	6,879	7,025	19,896	20,137
Surety segment | Commercial
Revenue by major product
Net premiums earned	6,521	5,857	18,968	17,285
Surety segment | Oil and Gas
Revenue by major product
Net premiums earned	$ 4,155	$ 4,559	$ 11,901	$ 13,813