INCOME TAXES (Details) (USD $)	3 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Tax discounting of claim reserves	$ 22,200,000	$ 25,462,000	$ 22,200,000	$ 25,462,000
Unearned premium offset	23,163,000	20,731,000	23,163,000	20,731,000
Deferred compensation	6,193,000	5,614,000	6,193,000	5,614,000
Stock option expense	4,160,000	4,678,000	4,160,000	4,678,000
NOL carryforward	1,059,000	3,223,000	1,059,000	3,223,000	5,500,000
Other	604,000	433,000	604,000	433,000
Deferred tax assets before allowance	57,379,000	60,141,000	57,379,000	60,141,000
Total deferred tax assets	57,379,000	60,141,000	57,379,000	60,141,000
Deferred tax liabilities:
Net unrealized appreciation of securities	73,198,000	77,036,000	73,198,000	77,036,000
Deferred policy acquisition costs	21,528,000	18,320,000	21,528,000	18,320,000
Book/tax depreciation	2,632,000	1,060,000	2,632,000	1,060,000
Intangible assets from CBIC acquisition	4,235,000	4,541,000	4,235,000	4,541,000
Undistributed earnings of unconsolidated investee	12,995,000	13,812,000	12,995,000	13,812,000
Other	592,000	938,000	592,000	938,000
Total deferred tax liabilities	115,180,000	115,707,000	115,180,000	115,707,000
Net deferred tax liability	(57,801,000)	(55,566,000)	(57,801,000)	(55,566,000)
U.S. federal tax rate (as a percent)			35.00%	35.00%	35.00%
Reconciliation of income tax expense attributable to income from operations with amounts computed by applying the U.S. federal tax rate to pretax income from continuing operations
Provision for income taxes at the statutory federal tax rates			61,483,000	49,956,000	64,255,000
Increase (reduction) in taxes resulting from:
Dividends received deduction			(2,490,000)	(2,630,000)	(1,980,000)
ESOP dividends paid deduction			(2,532,000)	(3,596,000)	(3,367,000)
Tax-exempt interest income			(3,758,000)	(2,995,000)	(2,412,000)
Unconsolidated investee dividends			3,696,000	1,848,000
Other items, net			404,000	499,000	492,000
Income tax expense:			49,411,000	39,386,000	56,988,000
Effective tax rates (as a percent)			28.10%	27.60%	31.00%
Tax benefit recognized from special dividend paid to ESOP			1,700,000	2,900,000	2,700,000
Effective rate reduction due to special dividend paid to ESOP (as a percent)			1.00%	2.00%	1.50%
Capital gains rate (as a percent)			35.00%
Dividend received	13,200,000	6,600,000	13,200,000	6,600,000
Lower tax rate (as a percent)			7.00%
Effective rate reduction due to dividend received (as a percent)			2.10%	1.30%
Expected effective tax rate when deferred items reverse in future years (as a percent)			35.00%
Federal and state income taxes paid			$ 36,800,000	$ 25,900,000	$ 50,500,000