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, 2014		$ 817,415	$ 25	$ 202,676	$ 523,541	$ 91,173
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased			0	(1,083)
Compensation expense and related tax benefit for stock-based award grants				360
Shares issued for stock-based awards			0	353
Net income		23,679			23,679
Dividends on common stock ($0.20 per share)					(4,997)
Change in net unrealized investment appreciation	[1]					7,292
Change in liability for underfunded employee benefit plans	[2]					1,214
All other changes in stockholders’ equity accounts		3,139
Balance, end of period at Mar. 31, 2015		$ 844,233	$ 25	$ 202,306	$ 542,223	$ 99,679

[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 reclassification adjustments and income taxes.