OPERATING SEGMENT INFORMATION (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenue by major product
Net premiums earned	$ 141,584	$ 130,826	$ 278,864	$ 246,877
Casualty
Revenue by major product
Net premiums earned	65,705	58,332	129,215	113,311
Casualty | General Liability
Revenue by major product
Net premiums earned	21,136	21,160	41,893	43,124
Casualty | Commercial and personal umbrella
Revenue by major product
Net premiums earned	16,747	15,713	32,907	31,285
Casualty | Commercial transportation
Revenue by major product
Net premiums earned	8,362	8,604	16,669	17,517
Casualty | P&C package business
Revenue by major product
Net premiums earned	6,956	4,109	13,855	4,109
Casualty | Executive products
Revenue by major product
Net premiums earned	3,942	3,663	7,752	7,185
Casualty | Professional services
Revenue by major product
Net premiums earned	6,650	2,572	12,318	4,761
Casualty | Specialty programs
Revenue by major product
Net premiums earned	633	1,089	1,338	2,429
Casualty | Other
Revenue by major product
Net premiums earned	1,279	1,422	2,483	2,901
Property
Revenue by major product
Net premiums earned	49,848	47,963	96,840	88,789
Property | Commercial property
Revenue by major product
Net premiums earned	18,093	20,386	36,645	40,599
Property | Marine
Revenue by major product
Net premiums earned	15,351	12,849	30,565	25,321
Property | Crop reinsurance
Revenue by major product
Net premiums earned	5,066	6,262	6,116	7,334
Property | Property reinsurance
Revenue by major product
Net premiums earned	5,980	4,580	13,367	8,369
Property | Other property
Revenue by major product
Net premiums earned	5,358	3,886	10,147	7,166
Surety
Revenue by major product
Net premiums earned	26,031	24,531	52,809	44,777
Surety | Miscellaneous
Revenue by major product
Net premiums earned	9,788	8,658	19,574	15,024
Surety | Contract
Revenue by major product
Net premiums earned	6,122	5,995	12,672	10,373
Surety | Commercial
Revenue by major product
Net premiums earned	5,557	5,321	10,962	10,383
Surety | Oil and gas
Revenue by major product
Net premiums earned	$ 4,564	$ 4,557	$ 9,601	$ 8,997