INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Tax discounting of claim reserves	$ 17,330	$ 17,866
Unearned premium offset	26,712	25,848
Deferred compensation	4,727	6,231
Stock option expense	4,114	4,482
Other	685	657
Deferred tax assets before allowance	53,568	55,084
Total deferred tax assets	53,568	55,084
Deferred tax liabilities:
Net unrealized appreciation of securities	66,973	67,740
Deferred policy acquisition costs	25,602	24,440
Book/tax depreciation	4,819	4,613
Intangible assets	1,980	3,878
Undistributed earnings of unconsolidated investees	18,397	17,888
Other	291	518
Total deferred tax liabilities	118,062	119,077
Net deferred tax liability	$ (64,494)	$ (63,993)
U.S. federal tax rate (as a percent)	35.00%	35.00%	35.00%
Reconciliation of income tax expense reported to amount computed by applying the U.S. federal tax rate
Provision for income taxes at the statutory rate of 35%	$ 54,979	$ 68,839	$ 66,320
Increase (reduction) in taxes resulting from:
Dividends received deduction	(2,216)	(2,278)	(2,390)
ESOP dividends paid deduction	(3,302)	(3,377)	(4,473)
Tax-exempt interest income	(4,263)	(4,214)	(4,118)
Unconsolidated investee dividends	(2,772)		(1,848)
Other items, net	(264)	168	551
Total tax expense	$ 42,162	$ 59,138	$ 54,042
Effective tax rates (as a percent)	26.80%	30.10%	28.50%
Capital gains rate (as a percent)	35.00%
Dividend received	$ 9,900		$ 6,600
Lower tax rate (as a percent)	7.00%		7.00%
Effective rate reduction due to dividend received (as a percent)	1.80%		1.00%
Effective rate reduction due to dividends paid to ESOP (as a percent)	2.10%	1.70%	2.40%
Expected effective tax rate when deferred items reverse in future years (as a percent)	35.00%
Federal and state income taxes paid	$ 26,900	$ 44,200	$ 48,500