Unaudited Condensed Consolidated Statements of Changes in Equity (USD $) In Thousands, unless otherwise specified	Total	Total Stockholders' Equity	Common Stock Common Class A	Common Stock Common Class B	Capital in Excess of Par Value	Retained Earnings	Foreign Currency Translation Adjustment	Deferred Gain (Loss) on Cash Flow Hedging	Pension and Postretirement Plan Adjustment	Noncontrolling Interest
Balance at Dec. 31, 2011	$ 577,092	$ 576,210	$ 6,778	$ 1,596	$ 22,786	$ 619,614	$ 13,230	$ 2,598	$ (90,392)	$ 882
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,061	1,061	20		1,041
Purchase of treasury shares	(577)	(577)	(6)		(571)
Conversion of Class B to Class A shares	0		3	(3)
Net income	25,250	25,250				25,250
Cash dividends	(4,466)	(4,466)				(4,466)
Current period other comprehensive income (loss)	10,285	10,285					10,821	(536)	0
Reclassification adjustment to net income	2,139	2,139						146	1,993
Net loss attributable to noncontrolling interest	(43)									(43)
Balance at Mar. 31, 2012	610,741	609,902	6,795	1,593	23,256	640,398	24,051	2,208	(88,399)	839
Balance at Dec. 31, 2012	281,331	281,331	6,771	1,582	24,612	313,450	13,640	7,499	(86,223)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	508	508	75		433
Purchase of treasury shares	(5,100)	(5,100)	(90)		(5,010)
Net income	4,422	4,422				4,422
Cash dividends	(2,102)	(2,102)				(2,102)
Current period other comprehensive income (loss)	843	843					723	120
Reclassification adjustment to net income	591	591						149	442
Balance at Mar. 31, 2013	$ 280,493	$ 280,493	$ 6,756	$ 1,582	$ 20,035	$ 315,770	$ 14,363	$ 7,768	$ (85,781)	$ 0