Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Total Stockholders' Equity	Common Stock Class A Common Stock	Common Stock Class B Common Stock	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, 2013		$ 297,780	$ 6,290	$ 1,581	$ 0	$ 302,168	$ (803)	$ 1,021	$ 676	$ (13,153)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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 on common stock		(7,755)				(7,755)
Current period other comprehensive income (loss)		(9,455)					(1,896)	442	(1,518)	(6,483)
Reclassification adjustment to net income (loss)		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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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 on common stock		(7,296)				(7,296)
Current period other comprehensive income (loss)		(4,520)					(2,756)	17	(577)	(1,204)
Reclassification adjustment to net income (loss)		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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation		5,337	51		5,286
Purchase of treasury shares		(6,044)	(109)		5,286	(649)
Conversion of Class B to Class A shares		0	1	(1)
Net income (loss)	$ 29,607	29,607				29,607
Cash dividends on common stock		(7,262)				(7,262)
Current period other comprehensive income (loss)		(3,928)					(2,078)	413	(252)	(2,011)
Reclassification adjustment to net income (loss)		1,445							757	688
Balance, end of period at Dec. 31, 2016		$ 220,293	$ 5,208	$ 1,571	$ 0	$ 239,441	$ (7,533)	$ 1,893	$ 393	$ (20,680)