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	2,170	2,170	21		2,149
Purchase of treasury shares	(577)	(577)	(6)		(571)
Conversion of Class B to Class A shares	0		6	(6)
Net income	46,962	46,962				46,962
Cash dividends	(9,058)	(9,058)				(9,058)
Current period other comprehensive income (loss)	(3,601)	(3,601)					(5,875)	2,274	0
Reclassification adjustment to net income	3,675	3,675						(222)	3,897
Net loss attributable to noncontrolling interest	45									45
Balance at Jun. 30, 2012	616,708	615,781	6,799	1,590	24,364	657,518	7,355	4,650	(86,495)	927
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	865	865	78		787
Purchase of treasury shares	(21,608)	(21,608)	(394)		(21,214)
Net income	9,569	9,569				9,569
Cash dividends	(4,134)	(4,134)				(4,134)
Current period other comprehensive income (loss)	925	925					228	697	0
Reclassification adjustment to net income	1,078	1,078						273	805
Balance at Jun. 30, 2013	$ 268,026	$ 268,026	$ 6,455	$ 1,582	$ 4,185	$ 318,885	$ 13,868	$ 8,469	$ (85,418)	$ 0