SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended		1 Months Ended			1 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 CBIC and Rockbridge	Jun. 30, 2014 CBIC and Rockbridge	Jun. 30, 2014 Surety segment Acquisitions prior to 2011	Apr. 30, 2011 Surety segment Contractors Bonding and Insurance Company	Apr. 30, 2011 Casualty and Surety segment Contractors Bonding and Insurance Company	Jun. 30, 2014 Casualty and Surety segment Contractors Bonding and Insurance Company	Apr. 30, 2011 Casualty Contractors Bonding and Insurance Company	Jun. 30, 2014 Casualty Contractors Bonding and Insurance Company	Jun. 30, 2014 Casualty Contractors Bonding and Insurance Company	Dec. 31, 2013 Casualty Rockbridge	Jun. 30, 2014 Casualty Rockbridge
INTANGIBLE ASSETS
Goodwill and intangibles	$ 74,407,000		$ 74,407,000		$ 74,876,000						$ 32,200,000					$ 16,000,000
Goodwill								26,200,000								12,400,000
Goodwill acquired									15,100,000			5,300,000
Indefinite Lived Intangible Assets Acquired										8,800,000
Impairment of goodwill													0	0	0
Impairment of indefinite-lived intangible assets													0	0
Definite-lived intangible assets, net of amortization											3,000,000					3,600,000
Amortization of intangible assets						300,000	500,000
Basic EPS, Income (Numerator)
Income available to common shareholders	35,725,000	29,902,000	64,694,000	54,749,000
Diluted EPS, Income (Numerator)
Income available to common shareholders	$ 35,725,000	$ 29,902,000	$ 64,694,000	$ 54,749,000
Basic EPS, Weighted Average Shares (Denominator)
Number of shares outstanding	43,001	42,628	42,993	42,587
Effect of Dilutive Securities, Shares (Denominator)
Stock options (in shares)	687	713	676	681
Diluted EPS, Weighted Average Shares (Denominator)
Number of shares outstanding	43,688	43,341	43,669	43,268
Basic EPS, Per Share Amount
Basic net earnings per share (in dollars per share)	$ 0.83	$ 0.70	$ 1.50	$ 1.29
Diluted EPS, Per Share Amount
Diluted earnings per share (in dollars per share)	$ 0.82	$ 0.69	$ 1.48	$ 1.27