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, 2010	$ 61	$ 367,448	$ 823,579	$ 96,582	$ (407,663)
Options exercised, 2012, 145,618 shares; 2011, 105,944 shares	1
Conversion of common stock units, 2012, 4,266 shares; 2011, 15,715 shares
Conversion of restricted stock units, 2012, 48,167 shares; 2011, 6,818 shares
Options exercised and conversion of common stock units and restricted stock units		2,145
Share-based compensation expense		410
Cumulative effect of change in accounting principle, net of taxes			(34,447)	1,531
Net income			25,807			25,807
Cash dividends, 2012, $0.13 per share; 2011, $0.11 per share			(4,554)
Change in net unrealized gains and losses on fixed maturities and equity securities				(3,770)		(3,770)
Change in net funded status of pension and other postretirement benefit obligations
Ending balance at Mar. 31, 2011	62	370,003	810,385	94,343	(407,663)	867,130
Beginning balance at Dec. 31, 2011	62	373,384	840,644	251,980	(410,717)	1,055,353
Conversion of common stock units, 2012, 4,266 shares; 2011, 15,715 shares
Conversion of restricted stock units, 2012, 48,167 shares; 2011, 6,818 shares
Options exercised and conversion of common stock units and restricted stock units		2,436
Share-based compensation expense		430
Net income			26,671			26,671
Cash dividends, 2012, $0.13 per share; 2011, $0.11 per share			(5,372)
Change in net unrealized gains and losses on fixed maturities and equity securities				12,583		12,583
Change in net funded status of pension and other postretirement benefit obligations
Acquisition of shares, 2012, 200,120 shares; 2011, 0 shares					(3,337)
Ending balance at Mar. 31, 2012	$ 62	$ 376,250	$ 861,943	$ 264,563	$ (414,054)	$ 1,088,764