ACQUISITIONS (Details) - 10K (USD $)	3 Months Ended								12 Months Ended			0 Months Ended		11 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 02, 2012	Feb. 05, 2014	Dec. 31, 2014
Business acquisition
Amount of investment									$ 5,301,000
Equity in earnings of unconsolidated investees									12,338,000	10,915,000	8,853,000
Reinsurance assumed									76,581,000	73,053,000	75,692,000
Direct premiums written									787,267,000	770,142,000	709,107,000
Net premiums earned	179,892,000	177,747,000	168,604,000	161,132,000	168,396,000	163,702,000	154,553,000	144,151,000	687,375,000	630,802,000	576,571,000
Casualty segment
Business acquisition
Net premiums earned									382,105,000	324,022,000	267,697,000
Surety segment
Business acquisition
Net premiums earned									107,494,000	106,639,000	106,472,000
Rockbridge
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
Present value of an earn-out agreement to be paid in future years	1,000,000								1,000,000			1,200,000		1,000,000
Direct premiums written									15,100,000	16,700,000
Net premiums earned									15,900,000	8,600,000
Prime Holdings Insurance Services, Inc. (Prime) [Member]
Business acquisition
Amount of investment													5,300,000
Equity ownership interest (as a percent)													20.00%
Equity in earnings of unconsolidated investees														300,000
Percentage of quota share reinsurance treaty, effective January 1, 2014									25.00%
Reinsurance assumed									10,200,000
Net premiums earned									$ 5,300,000