Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands		Total	Common stock	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	(29,784)
Shares issued for stock-based awards			0	2,960
Compensation expense and related tax benefit for stock-based award grants				3,456
Net income		5,030			5,030
Dividends on common stock ($0.81 per share)					(20,364)
Change in net unrealized investment appreciation	[1]					38,230
Change in liability for underfunded employee benefit plans	[2]					2,636
All other changes in stockholders’ equity accounts		(2,866)
Balance, end of period at Sep. 30, 2017		944,048	25	193,114	600,988	149,921
Balance, beginning of year at Jun. 30, 2017						136,968
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		(17,864)
Balance, end of period at Sep. 30, 2017		$ 944,048	$ 25	$ 193,114	$ 600,988	$ 149,921

[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.