Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands		Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss), net of tax
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle		$ (191,244)			$ 191,244	$ (191,244)
Balance, beginning of year at Dec. 31, 2017		973,373	$ 25	$ 196,334	608,700	168,314
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased			0	(5,404)
Shares issued for stock-based awards			0	2,293
Compensation expense and related tax benefit for stock-based award grants				1,281
Net income		45,759			45,759
Dividends on common stock ($0.28 per share)					(6,958)
Change in net unrealized investment appreciation and depreciation of discontinued operations, sold					(6,714)	(34,248)	[1]
Change in liability for underfunded employee benefit plans	[2]					1,311
All other changes in stockholders’ equity accounts		(48,439)
Balance, end of period at Mar. 31, 2018		$ 970,693	$ 25	$ 194,504	$ 832,031	$ (55,867)

[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.