Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Total Stockholders' Equity	Common Stock Shares Outstanding Class A	Common Stock Shares Outstanding Class B	Capital in Excess of Par Value	Retained Earnings	Foreign Currency Translation Adjustment	Deferred Gain (Loss) on Available for Sale Securities	Deferred Gain (Loss) on Cash Flow Hedging	Pension and Postretirement Plan Adjustment
Balance, beginning of period at Dec. 31, 2012		$ 281,331	$ 6,771	$ 1,582	$ 24,612	$ 270,227	$ (574)	$ 292	$ (286)	$ (21,293)
Stockholders’ equity
Stock-based compensation		1,807	83		1,724
Purchase of treasury shares		(31,306)	(565)		(26,336)	(4,405)
Conversion of Class B to Class A shares		0	1	(1)
Net income (loss)	$ 44,450	44,450				44,450
Cash dividends		(8,104)				(8,104)
Current period other comprehensive income (loss)		9,332					(229)	729	810	8,022
Current period curtailment gain		(983)								(983)
Reclassification adjustment to net income		1,253							(152)	(1,101)
Balance, end of period at Dec. 31, 2013		297,780	6,290	1,581	0	302,168	(803)	1,021	676	(13,153)
Stockholders’ equity
Stock-based compensation		2,572	28		2,544
Purchase of treasury shares		(35,075)	(664)		(2,544)	(31,867)
Conversion of Class B to Class A shares		0	8	(8)
Net income (loss)	(38,118)	(38,118)				(38,118)
Cash dividends		(7,755)				(7,755)
Current period other comprehensive income (loss)		(9,455)				0	(1,896)	442	(1,518)	(6,483)
Reclassification adjustment to net income		1,525							898	627
Balance, end of period at Dec. 31, 2014		211,474	5,662	1,573	0	224,428	(2,699)	1,463	56	(19,009)
Stockholders’ equity
Stock-based compensation		2,241	45		2,196
Purchase of treasury shares		(24,010)	(443)		(2,196)	(21,371)
Conversion of Class B to Class A shares		0	1	(1)
Net income (loss)	$ 21,984	21,984				21,984
Cash dividends		(7,296)				(7,296)
Current period other comprehensive income (loss)		(4,520)					(2,756)	17	(577)	(1,204)
Reclassification adjustment to net income		1,265							409	856
Balance, end of period at Dec. 31, 2015		$ 201,138	$ 5,265	$ 1,572	$ 0	$ 217,745	$ (5,455)	$ 1,480	$ (112)	$ (19,357)