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	6,391
Compensation expense and related tax benefit for stock-based award grants				4,040
Net income		56,986			56,986
Dividends on common stock ($3.90 per share)					(97,635)
Change in net unrealized investment appreciation and depreciation of discontinued operations, sold					(6,714)	(50,756)	[1]
Change in liability for underfunded employee benefit plans	[2]					3,935
All other changes in stockholders’ equity accounts		(146,143)
Balance, end of period at Sep. 30, 2018		884,216	25	201,361	752,581	(69,751)
Balance, beginning of year at Jun. 30, 2018						(59,298)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		11,070
Balance, end of period at Sep. 30, 2018		$ 884,216	$ 25	$ 201,361	$ 752,581	$ (69,751)

[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.