Consolidated Statement of Stockholders' Equity (USD $) In Thousands, unless otherwise specified		Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income, Net of Tax [Member]
Balance, beginning of year at Dec. 31, 2010		$ 716,424	$ 26	$ 223,439	$ 415,981	$ 76,978
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation expense and related tax benefit for stock-based award grants				1,830
Shares repurchased			(1)	(12,432)
Shares issued for stock-based awards			0	208
Net income		11			11
Dividends on common stock ($0.69 per share in 2013; $0.60 per share in 2012 and 2011)					(15,507)
Change in net unrealized investment appreciation	[1]					21,727
Change in liability for underfunded employee benefit plans	[2]					(16,119)
All other changes in stockholders' equity accounts		(20,294)
Balance, end of year at Dec. 31, 2011		696,141	25	213,045	400,485	82,586
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation expense and related tax benefit for stock-based award grants				1,686
Shares repurchased			0	(7,301)
Shares issued for stock-based awards			0	1,106
Net income		40,212			40,212
Dividends on common stock ($0.69 per share in 2013; $0.60 per share in 2012 and 2011)					(15,269)
Change in net unrealized investment appreciation	[1]					19,720
Change in liability for underfunded employee benefit plans	[2]					(7,118)
All other changes in stockholders' equity accounts		(7,176)
Balance, end of year at Dec. 31, 2012		729,177	25	208,536	425,428	95,188
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation expense and related tax benefit for stock-based award grants				1,289
Shares repurchased			0	(1,644)
Shares issued for stock-based awards			0	3,393
Net income		76,140			76,140
Dividends on common stock ($0.69 per share in 2013; $0.60 per share in 2012 and 2011)					(17,484)
Change in net unrealized investment appreciation	[1]					(27,495)
Change in liability for underfunded employee benefit plans	[2]					19,457
All other changes in stockholders' equity accounts		(22,484)
Balance, end of year at Dec. 31, 2013		$ 782,833	$ 25	$ 211,574	$ 484,084	$ 87,150

[1] The change in net unrealized appreciation is net of reclassification adjustments and income taxes.

[2] The change in liability for underfunded employee benefit plans is net of income taxes.