ACQUISITIONS (Details) (USD $)	3 Months Ended								12 Months Ended									3 Months Ended	12 Months Ended		0 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	Dec. 31, 2013 Casualty	Dec. 31, 2012 Casualty	Dec. 31, 2011 Casualty	Dec. 31, 2013 Surety	Dec. 31, 2012 Surety	Dec. 31, 2011 Surety	Dec. 31, 2012 Rockbridge	Dec. 31, 2013 Rockbridge	Nov. 02, 2012 Rockbridge state	Apr. 28, 2011 Contractors Bonding and Insurance Company	Dec. 31, 2013 Contractors Bonding and Insurance Company	Dec. 31, 2012 Contractors Bonding and Insurance Company	Dec. 31, 2011 Contractors Bonding and Insurance Company	Dec. 31, 2013 Contractors Bonding and Insurance Company Casualty	Dec. 31, 2013 Contractors Bonding and Insurance Company Surety
Business acquisition
Number of states in which coverage is offered to individual physicians and physician groups																				50
Total business acquisition consideration																		$ 16,700,000
Business acquisition consideration paid in cash																		15,500,000			135,900,000
Present value of an earn-out agreement to be paid in future years																		1,200,000	1,300,000
Gross premiums written																			16,700,000			55,400,000	54,900,000	36,000,000	37,000,000	18,400,000
Net premiums earned	168,396,000	163,702,000	154,553,000	144,151,000	147,764,000	149,943,000	141,584,000	137,280,000	630,802,000	576,571,000	538,452,000	324,022,000	267,697,000	236,198,000	106,639,000	106,472,000	98,594,000		8,600,000
Pretax earnings contributed																						$ 12,500,000	$ 14,100,000	$ 2,700,000