OPERATING SEGMENT INFORMATION (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenue by major product
Net premiums earned	$ 144,151	$ 137,280
Casualty
Revenue by major product
Net premiums earned	72,969	63,510
Casualty | General liability
Revenue by major product
Net premiums earned	20,777	20,757
Casualty | Commercial and personal umbrella
Revenue by major product
Net premiums earned	18,950	16,160
Casualty | Commercial transportation
Revenue by major product
Net premiums earned	9,934	8,307
Casualty | P&C package business
Revenue by major product
Net premiums earned	7,421	6,899
Casualty | Executive products
Revenue by major product
Net premiums earned	4,346	3,810
Casualty | Professional services
Revenue by major product
Net premiums earned	9,009	5,668
Casualty | Specialty programs
Revenue by major product
Net premiums earned	504	705
Casualty | Medical professional liability
Revenue by major product
Net premiums earned	750
Casualty | Other
Revenue by major product
Net premiums earned	1,278	1,204
Property
Revenue by major product
Net premiums earned	44,981	46,992
Property | Commercial property
Revenue by major product
Net premiums earned	19,616	18,552
Property | Marine
Revenue by major product
Net premiums earned	14,614	15,214
Property | Crop reinsurance
Revenue by major product
Net premiums earned	1,267	1,050
Property | Property reinsurance
Revenue by major product
Net premiums earned	5,272	7,387
Property | Other property
Revenue by major product
Net premiums earned	4,212	4,789
Surety
Revenue by major product
Net premiums earned	26,201	26,778
Surety | Miscellaneous
Revenue by major product
Net premiums earned	9,481	9,786
Surety | Contract
Revenue by major product
Net premiums earned	6,459	6,550
Surety | Commercial
Revenue by major product
Net premiums earned	5,711	5,405
Surety | Oil and gas
Revenue by major product
Net premiums earned	$ 4,550	$ 5,037