Consolidated Statements Of Changes In Shareholders' Equity (USD $) In Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net Of Taxes [Member]	Treasury Stock, At Cost [Member]	Total
Beginning balance at Dec. 31, 2008	$ 61	$ 355,542	$ 694,492	$ (193,587)	$ (407,663)
Conversion of common stock units, 2011, 15,715 shares; 2010, 160,876 shares; 2009, 84,562 shares
Conversion of restricted stock units, 2011, 182,309 shares; 2010, 47,149 shares; 2009, 38,371 shares
Options exercised and conversion of common stock units and restricted stock units		1,366
Share-based compensation expense		1,173
Net income			73,486			73,486
Cash dividends, 2011, $0.46 per share; 2010, $0.35 per share; 2009,$0.2375 per share			(9,635)
Change in net unrealized gains and losses on fixed maturities and equity securities				204,331		204,331
Change in net funded status of pension and other postretirement benefit obligations				(21)		(21)
Ending balance at Dec. 31, 2009	61	358,081	758,343	10,723	(407,663)	719,545
Conversion of common stock units, 2011, 15,715 shares; 2010, 160,876 shares; 2009, 84,562 shares
Conversion of restricted stock units, 2011, 182,309 shares; 2010, 47,149 shares; 2009, 38,371 shares
Options exercised and conversion of common stock units and restricted stock units		7,204
Share-based compensation expense		2,163
Cumulative effect of adoption of accounting principle, net of taxes			(1,338)	1,338
Net income			80,862			80,862
Cash dividends, 2011, $0.46 per share; 2010, $0.35 per share; 2009,$0.2375 per share			(14,288)
Change in net unrealized gains and losses on fixed maturities and equity securities				86,133		86,133
Change in net funded status of pension and other postretirement benefit obligations				(1,612)		(1,612)
Ending balance at Dec. 31, 2010	61	367,448	823,579	96,582	(407,663)	880,007
Options exercised, 2011, 136,290 shares; 2010, 263,206 shares; 2009, 0 shares	1
Conversion of common stock units, 2011, 15,715 shares; 2010, 160,876 shares; 2009, 84,562 shares
Conversion of restricted stock units, 2011, 182,309 shares; 2010, 47,149 shares; 2009, 38,371 shares
Options exercised and conversion of common stock units and restricted stock units		4,485
Share-based compensation expense		1,451
Net income			70,480			70,480
Cash dividends, 2011, $0.46 per share; 2010, $0.35 per share; 2009,$0.2375 per share			(18,990)
Change in net unrealized gains and losses on fixed maturities and equity securities				155,633		155,633
Change in net funded status of pension and other postretirement benefit obligations				(3,087)		(3,087)
Acquisition of 214,834 shares in 2011; 0 shares in 2010 and 2009					(3,054)
Ending balance at Dec. 31, 2011	$ 62	$ 373,384	$ 875,069	$ 249,128	$ (410,717)	$ 1,086,926