Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (USD $) In Thousands	Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss), net of taxes	Treasury stock, at cost
Beginning balance at Dec. 31, 2010		$ 61	$ 367,448	$ 823,579	$ 96,582	$ (407,663)
Options exercised, 2012, 297,592 shares; 2011, 136,290 shares		1
Options exercised and conversion of common stock units and restricted stock units			4,247
Share-based compensation expense			1,229
Cumulative effect of change in accounting principle, net of taxes				(34,447)	1,531
Net income	37,593			37,593
Cash dividends, 2012, $0.39 per share; 2011, $0.33 per share				(13,634)
Change in net unrealized gains and losses on fixed maturities and equity securities	148,738				148,738
Acquisition of shares, 2012, 801,086 shares; 2011, 60,126 shares						(1,007)
Total shareholders' equity	1,024,258	62	372,924	813,091	246,851	(408,670)
Ending balance at Sep. 30, 2011	1,024,258	62	372,924	813,091	246,851	(408,670)
Beginning balance at Dec. 31, 2011	1,055,353	62	373,384	840,644	251,980	(410,717)
Options exercised, 2012, 297,592 shares; 2011, 136,290 shares
Conversion of common stock units, 2012, 15,084 shares; 2011, 15,715 shares
Conversion of restricted stock units, 2012, 91,327 shares; 2011, 170,876 shares
Options exercised and conversion of common stock units and restricted stock units			5,480
Share-based compensation expense			1,207
Cumulative effect of change in accounting principle, net of taxes
Net income	72,040			72,040
Cash dividends, 2012, $0.39 per share; 2011, $0.33 per share				(16,001)
Change in net unrealized gains and losses on fixed maturities and equity securities	127,979				127,979
Change in net funded status of pension and other postretirement benefit obligations
Acquisition of shares, 2012, 801,086 shares; 2011, 60,126 shares						(13,640)
Total shareholders' equity	1,232,418	62	380,071	896,683	379,959	(424,357)
Ending balance at Sep. 30, 2012	$ 1,232,418	$ 62	$ 380,071	$ 896,683	$ 379,959	$ (424,357)