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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 5) - 10K (USD $)	3 Months Ended								12 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
INTANGIBLE ASSETS
Goodwill and intangibles	$ 72,695,000				$ 74,876,000				$ 72,695,000	$ 74,876,000
Basic EPS, Income (Numerator)
Income available to common shareholders	37,497,000	33,254,000	35,725,000	28,969,000	33,859,000	37,647,000	29,902,000	24,847,000	135,445,000	126,255,000	103,346,000
Diluted EPS, Income (Numerator)
Income available to common shareholders									135,445,000	126,255,000	103,346,000
Basic EPS, Weighted Average Shares (Denominator)
Number of shares outstanding									43,020	42,744	42,431
Effect of Dilutive Securities, Shares (Denominator)
Stock options (in shares)									799	770	729
Diluted EPS, Weighted Average Shares (Denominator)
Number of shares outstanding									43,819	43,514	43,160
Basic EPS, Per Share Amount
Basic net earnings per share (in dollars per share)	$ 0.87us-gaap_EarningsPerShareBasic	$ 0.77us-gaap_EarningsPerShareBasic	$ 0.83us-gaap_EarningsPerShareBasic	$ 0.67us-gaap_EarningsPerShareBasic	$ 0.79us-gaap_EarningsPerShareBasic	$ 0.88us-gaap_EarningsPerShareBasic	$ 0.70us-gaap_EarningsPerShareBasic	$ 0.58us-gaap_EarningsPerShareBasic	$ 3.15us-gaap_EarningsPerShareBasic	$ 2.95us-gaap_EarningsPerShareBasic	$ 2.44us-gaap_EarningsPerShareBasic
Diluted EPS, Per Share Amount
Diluted earnings per share (in dollars per share)	$ 0.85us-gaap_EarningsPerShareDiluted	$ 0.76us-gaap_EarningsPerShareDiluted	$ 0.82us-gaap_EarningsPerShareDiluted	$ 0.66us-gaap_EarningsPerShareDiluted	$ 0.77us-gaap_EarningsPerShareDiluted	$ 0.86us-gaap_EarningsPerShareDiluted	$ 0.69us-gaap_EarningsPerShareDiluted	$ 0.57us-gaap_EarningsPerShareDiluted	$ 3.09us-gaap_EarningsPerShareDiluted	$ 2.90us-gaap_EarningsPerShareDiluted	$ 2.39us-gaap_EarningsPerShareDiluted
COMPREHENSIVE EARNINGS
Tax rate used (as a percent)									35.00%	35.00%	35.00%
Other comprehensive income (loss), tax									19,000,000us-gaap_OtherComprehensiveIncomeLossTax	(3,800,000)us-gaap_OtherComprehensiveIncomeLossTax	13,900,000us-gaap_OtherComprehensiveIncomeLossTax
Acquisitions prior to 2011
INTANGIBLE ASSETS
Goodwill and intangibles	26,200,000								26,200,000
Goodwill	25,600,000								25,600,000
Indefinite-Lived Intangible Assets (Excluding Goodwill)	600,000								600,000
Contractors Bonding and Insurance Company
INTANGIBLE ASSETS
Goodwill and intangibles	30,600,000								30,600,000
Indefinite-Lived Intangible Assets (Excluding Goodwill)	7,500,000								7,500,000
Definite-lived intangible assets, net of amortization	2,700,000								2,700,000
Impairment of intangible asset									1,300,000
Rockbridge
INTANGIBLE ASSETS
Goodwill and intangibles	15,900,000								15,900,000
Definite-lived intangible assets, net of amortization	3,500,000								3,500,000
CBIC and Rockbridge
INTANGIBLE ASSETS
Amortization of intangible assets									900,000	1,200,000	1,000,000
Surety segment \| Contractors Bonding and Insurance Company
INTANGIBLE ASSETS
Goodwill	15,100,000								15,100,000
Casualty segment \| Contractors Bonding and Insurance Company
INTANGIBLE ASSETS
Goodwill	5,300,000								5,300,000
Casualty segment \| Rockbridge
INTANGIBLE ASSETS
Goodwill	$ 12,400,000								$ 12,400,000