OPERATING SEGMENT INFORMATION (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue by major product
Net premiums earned	$ 168,396	$ 163,702	$ 154,553	$ 144,151	$ 147,764	$ 149,943	$ 141,584	$ 137,280	$ 630,802	$ 576,571	$ 538,452
Casualty
Revenue by major product
Net premiums earned									324,022	267,697	236,198
Casualty | Commercial and personal umbrella
Revenue by major product
Net premiums earned									85,532	68,287	63,020
Casualty | General liability
Revenue by major product
Net premiums earned									81,427	84,985	85,020
Casualty | Commercial transportation
Revenue by major product
Net premiums earned									50,287	34,701	34,106
Casualty | Professional services
Revenue by major product
Net premiums earned									42,063	28,018	13,151
Casualty | P&C package business
Revenue by major product
Net premiums earned									30,603	28,497	16,379
Casualty | Executive products
Revenue by major product
Net premiums earned									19,123	17,198	15,472
Casualty | Medical professional liability
Revenue by major product
Net premiums earned									8,626	25
Casualty | Other casualty
Revenue by major product
Net premiums earned									6,361	5,986	9,050
Property
Revenue by major product
Net premiums earned									200,141	202,402	203,660
Property | Commercial property
Revenue by major product
Net premiums earned									76,939	74,197	80,743
Property | Marine
Revenue by major product
Net premiums earned									57,122	56,367	51,654
Property | Crop reinsurance
Revenue by major product
Net premiums earned									31,421	24,506	34,935
Property | Property reinsurance
Revenue by major product
Net premiums earned									15,770	27,021	19,925
Property | Other property
Revenue by major product
Net premiums earned									18,889	20,311	16,403
Surety
Revenue by major product
Net premiums earned									106,639	106,472	98,594
Surety | Miscellaneous
Revenue by major product
Net premiums earned									38,131	39,299	34,837
Surety | Contract
Revenue by major product
Net premiums earned									27,176	26,329	24,354
Surety | Commercial
Revenue by major product
Net premiums earned									23,133	22,107	21,317
Surety | Oil and Gas
Revenue by major product
Net premiums earned									$ 18,199	$ 18,737	$ 18,086