Condensed Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Capital In Excess of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Stockholders' Equity [Member]	Non-Controlling Interest [Member]
Balance at Dec. 31, 2012	$ 1,002,916	$ 1,196	$ 713,257	$ 349,063	$ 32,728	$ (109,809)	$ 986,435	$ 16,481
Balance, Shares at Dec. 31, 2012		119,608,026
Net Income	114,577			120,044			120,044	(5,467)
Dividends declared	(18,147)			(18,147)			(18,147)
Defined benefit obligations	993				993		993
Available-for-sale investments	(593)				(593)		(593)
Currency translation adjustments	(7,568)				(7,564)		(7,564)	(4)
Derivative financial instruments	(1,579)				(1,579)		(1,579)
Exercise of stock options	1,874	2	1,872				1,874
Exercise of stock options, Shares		101,157
Contributions to thrift plan	6,532	2	6,530				6,532
Contributions to thrift plan, shares		233,766
Shares placed in treasury	(127,773)					(127,773)	(127,773)
Stock-based compensation charges	9,076	2	9,074				9,076
Stock-based compensation charges, Shares		217,563
Contribution of in-kind services	7,369							7,369
Distributions to noncontrolling interests	(326)							(326)
Balance at Jun. 30, 2013	987,351	1,202	730,733	450,960	23,985	(237,582)	969,298	18,053
Balance, Shares at Jun. 30, 2013		120,160,512
Balance at Dec. 31, 2013	1,182,941	1,205	747,189	656,916	28,348	(268,971)	1,164,687	18,254
Balance, Shares at Dec. 31, 2013	120,536,910	120,536,910
Net Income	64,646			71,481			71,481	(6,835)
Dividends declared	(22,235)			(22,235)			(22,235)
Defined benefit obligations	794				794		794
Available-for-sale investments	77				77		77
Currency translation adjustments	(7,142)				(7,138)		(7,138)	(4)
Derivative financial instruments	(189)				(189)		(189)
Exercise of stock options	3,520	1	3,519				3,520
Exercise of stock options, Shares		135,649
Contributions to thrift plan	6,556	2	6,554				6,556
Contributions to thrift plan, shares		196,297
Shares placed in treasury	(104,805)					(104,805)	(104,805)
Stock-based compensation charges	7,411	5	7,406				7,411
Stock-based compensation charges, Shares		419,004
Contribution of in-kind services	5,830							5,830
Distributions to noncontrolling interests	(409)							(409)
Balance at Jun. 30, 2014	$ 1,136,995	$ 1,213	$ 764,668	$ 706,162	$ 21,892	$ (373,776)	$ 1,120,159	$ 16,836
Balance, Shares at Jun. 30, 2014	121,287,860	121,287,860