OPERATING SEGMENT INFORMATION Major Products (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenue by major product
Net premiums earned	$ 179,448	$ 177,747	$ 520,790	$ 507,483
Casualty segment
Revenue by major product
Net premiums earned	105,160	96,181	305,842	281,518
Casualty segment | Commercial and personal umbrella
Revenue by major product
Net premiums earned	26,500	25,256	77,809	75,036
Casualty segment | General liability
Revenue by major product
Net premiums earned	20,146	20,095	60,725	60,550
Casualty segment | Commercial transportation
Revenue by major product
Net premiums earned	17,464	14,677	47,262	44,193
Casualty segment | Professional services
Revenue by major product
Net premiums earned	18,140	15,227	52,861	41,927
Casualty segment | P&C package business
Revenue by major product
Net premiums earned	10,257	8,969	29,815	25,747
Casualty segment | Executive products
Revenue by major product
Net premiums earned	4,459	4,760	13,745	14,165
Casualty segment | Medical professional liability
Revenue by major product
Net premiums earned	3,032	3,546	9,168	10,970
Casualty segment | Other casualty
Revenue by major product
Net premiums earned	5,162	3,651	14,457	8,930
Property segment
Revenue by major product
Net premiums earned	44,685	54,143	128,084	146,252
Property segment | Commercial property
Revenue by major product
Net premiums earned	18,546	20,188	57,498	60,675
Property segment | Marine
Revenue by major product
Net premiums earned	12,029	12,115	34,930	37,278
Property segment | Crop reinsurance
Revenue by major product
Net premiums earned	4,523	11,802	6,210	18,671
Property segment | Specialty Personal
Revenue by major product
Net premiums earned	6,535	6,947	19,982	19,764
Property segment | Property reinsurance
Revenue by major product
Net premiums earned	3,029	2,997	9,388	9,745
Property segment | Other property
Revenue by major product
Net premiums earned	23	94	76	119
Surety segment
Revenue by major product
Net premiums earned	29,603	27,423	86,864	79,713
Surety segment | Miscellaneous
Revenue by major product
Net premiums earned	10,659	9,868	31,316	28,948
Surety segment | Contract
Revenue by major product
Net premiums earned	7,472	6,879	21,091	19,896
Surety segment | Commercial surety product
Revenue by major product
Net premiums earned	7,546	6,521	22,039	18,968
Surety segment | Oil and Gas
Revenue by major product
Net premiums earned	$ 3,926	$ 4,155	$ 12,418	$ 11,901