Consolidated Statement of Stockholders' Equity (Unaudited) (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, 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				859
Shares repurchased (101,901 shares)			(1)	(2,133)
Shares issued for stock-based awards			1	400
Net income		33,900			33,900
Dividends on common stock ($0.30 per share)					(7,641)
Change in net unrealized investment appreciation	[1]					12,292
Change in liability for underfunded employee benefit plans						1,544
All other changes in stockholders’ equity accounts		5,321
Balance, end of year at Jun. 30, 2012		$ 735,362	$ 25	$ 212,171	$ 426,744	$ 96,422

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