Consolidated Statement of Stockholders' Equity (USD $) In Thousands, unless otherwise specified		Total	Common Stocks [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income, Net of Tax [Member]
Balance, beginning of year at Dec. 31, 2009		$ 672,735	$ 26	$ 227,820	$ 384,242	$ 60,647
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation expense and related tax benefit for stock-based award grants				1,801
Shares repurchased			0	(6,280)
Shares issued for stock-based awards			0	98
Net income		47,513			47,513
Dividends on common stock ($0.60 per share per year)					(15,774)
Change in net unrealized investment appreciation	[1]					20,158
Change in liability for underfunded employee benefit plans	[2]					(3,827)
All other changes in stockholders' equity accounts		(3,824)
Balance, end 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 ($0.60 per share per year)					(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 ($0.60 per share per year)					(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

[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.