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, 2016		$ 941,884	$ 25	$ 216,482	$ 616,322	$ 109,055
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased			0	(21,184)
Shares issued for stock-based awards			0	2,207
Compensation expense and related tax benefit for stock-based award grants				2,254
Net income		22,894			22,894
Dividends on common stock ($0.53 per share)					(13,380)
Change in net unrealized investment appreciation	[1]					26,156
Change in liability for underfunded employee benefit plans	[2]					1,757
All other changes in stockholders’ equity accounts		(2,190)
Balance, end of period at Jun. 30, 2017		962,588	25	199,759	625,836	136,968
Balance, beginning of year at Mar. 31, 2017						117,448
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		2,958
Balance, end of period at Jun. 30, 2017		$ 962,588	$ 25	$ 199,759	$ 625,836	$ 136,968

[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.