CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Capital in Excess of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2015	$ 47,872	$ 93,247	$ 291,481	$ (6,474)	$ (34,147)	$ 391,979
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	0	0	31,448	0	0	31,448
Other comprehensive income (loss), net of tax	0	0	0	243	0	243
Cash dividends paid	0	0	(7,705)	0	0	(7,705)
Purchase of treasury stock	0	0	0	0	(377)	(377)
Stock-based compensation and related tax benefits	0	2,199	0	0	674	2,873
Employee Stock Ownership Plan	0	455	0	0	1,566	2,021
Balance at Jun. 30, 2016	47,872	95,901	315,224	(6,231)	(32,284)	420,482
Balance at Mar. 31, 2016				(4,531)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings						19,244
Other comprehensive income (loss), net of tax						(1,700)
Balance at Jun. 30, 2016	$ 47,872	$ 95,901	$ 315,224	$ (6,231)	$ (32,284)	$ 420,482