Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands		Total	Common stocks	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income, Net of Tax
Balance, beginning of year at Dec. 31, 2015		$ 878,897	$ 25	$ 207,426	$ 591,009	$ 80,437
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased			0	(2,867)
Shares issued for stock-based awards			0	7,149
Compensation expense and related tax benefit for stock-based award grants				2,249
Net income		37,909			37,909
Dividends on common stock ($0.72 per share)					(18,246)
Change in net unrealized investment appreciation	[1]					51,415
Change in liability for underfunded employee benefit plans	[2]					2,674
All other changes in stockholders’ equity accounts		42,374
Balance, end of period at Sep. 30, 2016		959,180	25	213,957	610,672	134,526
Balance, beginning of year at Jun. 30, 2016						141,279
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		12,368
Balance, end of period at Sep. 30, 2016		$ 959,180	$ 25	$ 213,957	$ 610,672	$ 134,526

[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.