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, beginning of period 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	2,757	2,757	26		2,731
Purchase of treasury shares	(577)	(577)	(6)		(571)
Conversion of Class B to Class A shares	0		6	(6)
Net income	85,066	85,066				85,066
Cash dividends	(13,651)	(13,651)				(13,651)
Stock dividend	(370,614)	(369,732)				(369,732)				(882)
Current period other comprehensive income (loss)	8,058	8,058					575	7,483
Current period curtailment gain	0
Reclassification adjustment to net income	3,015	3,015						(2,808)	5,823
Balance, end of period at Sep. 30, 2012	291,146	291,146	6,804	1,590	24,946	321,297	13,805	7,273	(84,569)	0
Balance, beginning of period 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	1,230	1,230	80		1,150
Purchase of treasury shares	(27,355)	(27,355)	(495)		(25,395)	(1,465)
Conversion of Class B to Class A shares	0		1	(1)
Net income	21,894	21,894				21,894
Cash dividends	(6,133)	(6,133)				(6,133)
Current period other comprehensive income (loss)	4,583	4,583					358	573	3,652
Current period curtailment gain	(1,123)	(1,123)							(1,123)
Reclassification adjustment to net income	1,294	1,294						235	(1,059)
Balance, end of period at Sep. 30, 2013	$ 275,721	$ 275,721	$ 6,357	$ 1,581	$ 367	$ 327,746	$ 13,998	$ 8,307	$ (82,635)	$ 0