OPERATING SEGMENT INFORMATION Major Products (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue by major product
Net premiums earned	$ 172,339	$ 168,604	$ 341,342	$ 329,736
Casualty segment
Revenue by major product
Net premiums earned	101,914	94,360	200,682	185,337
Casualty segment | Commercial and personal umbrella
Revenue by major product
Net premiums earned	26,012	25,024	51,309	49,780
Casualty segment | General liability
Revenue by major product
Net premiums earned	20,607	20,523	40,579	40,455
Casualty segment | Commercial transportation
Revenue by major product
Net premiums earned	15,117	15,005	29,798	29,516
Casualty segment | Professional services
Revenue by major product
Net premiums earned	17,641	13,839	34,721	26,700
Casualty segment | P&C package business
Revenue by major product
Net premiums earned	9,909	8,495	19,558	16,778
Casualty segment | Executive products
Revenue by major product
Net premiums earned	4,601	4,721	9,286	9,405
Casualty segment | Medical professional liability
Revenue by major product
Net premiums earned	3,032	3,724	6,136	7,424
Casualty segment | Other casualty
Revenue by major product
Net premiums earned	4,995	3,029	9,295	5,279
Property segment
Revenue by major product
Net premiums earned	41,281	48,791	83,399	92,109
Property segment | Commercial property
Revenue by major product
Net premiums earned	19,049	20,054	38,952	40,487
Property segment | Marine
Revenue by major product
Net premiums earned	10,984	12,962	22,901	25,163
Property segment | Crop reinsurance
Revenue by major product
Net premiums earned	1,222	5,683	1,687	6,869
Property segment | Specialty Personal
Revenue by major product
Net premiums earned	6,657	6,709	13,447	12,817
Property segment | Property reinsurance
Revenue by major product
Net premiums earned	3,342	3,387	6,359	6,748
Property segment | Other property
Revenue by major product
Net premiums earned	27		53	25
Net premiums earned		(4)
Surety segment
Revenue by major product
Net premiums earned	29,144	25,453	57,261	52,290
Surety segment | Miscellaneous
Revenue by major product
Net premiums earned	10,489	9,598	20,657	19,080
Surety segment | Contract
Revenue by major product
Net premiums earned	6,789	6,256	13,619	13,017
Surety segment | Commercial surety product
Revenue by major product
Net premiums earned	7,592	6,313	14,493	12,447
Surety segment | Oil and Gas
Revenue by major product
Net premiums earned	$ 4,274	$ 3,286	$ 8,492	$ 7,746