Consolidated Statements of Equity (Unaudited) (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Restricted Stock [Member]	Restricted Stock [Member] Common Stock [Member]	Restricted Stock [Member] Additional Paid-in Capital [Member]	Restricted Stock [Member] Retained Earnings [Member]	Restricted Stock [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Restricted Stock [Member] Noncontrolling Interest [Member]	Restricted Stock Units (RSUs) [Member]	Restricted Stock Units (RSUs) [Member] Common Stock [Member]	Restricted Stock Units (RSUs) [Member] Additional Paid-in Capital [Member]	Restricted Stock Units (RSUs) [Member] Retained Earnings [Member]	Restricted Stock Units (RSUs) [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Restricted Stock Units (RSUs) [Member] Noncontrolling Interest [Member]
Balance at Dec. 31, 2011	$ 648,989	$ 394	$ 260,680	$ 373,796	$ 5,862	$ 8,257
Balance (in Shares) at Dec. 31, 2011	39,352,375
Net Income	37,766	0	0	37,766	0
Net Income	2,057					2,057
Net income	39,823
Issuance of common stock upon stock option exercises including tax benefit	563	1	562	0	0	0
Issuance of common stock upon stock option exercises including tax benefit (in Shares)	26,776
Restricted shares issued							3	3	0	0	0	0	0	0	0	0	0	0
Restricted shares issued (in Shares)							266,715						14,446
Issuance of shares pursuant to deferred stock unit awards (in Shares)	34,132
Forfeitures of restricted shares (in Shares)	(30,599)
Shares repurchased and retired	(6,354)	(5)	(6,349)	0	0	0
Shares repurchased and retired (in Shares)	(384,890)
Equity-based compensation expense	5,246	0	5,246	0	0	0
Investment by non-controlling interests	4,939	0	0	0	0	4,939
Currency translation adjustment and derivative transactions, net	4,202	0	0	0	3,866	336
Balance at Sep. 30, 2012	697,411	393	260,139	411,562	9,728	15,589
Balance (in Shares) at Sep. 30, 2012	39,278,955
Balance at Dec. 31, 2012	716,120	390	257,209	426,457	15,260	16,804
Balance (in Shares) at Dec. 31, 2012	38,952,561
Net Income	29,862	0	0	29,862	0
Net Income	959					959
Net income	30,821
Issuance of common stock upon stock option exercises including tax benefit	899	0	899	0	0	0
Issuance of common stock upon stock option exercises including tax benefit (in Shares)	29,511
Restricted shares issued							4	4	0	0	0	0	0	0	0	0	0	0
Restricted shares issued (in Shares)							431,877						11,112
Issuance of shares pursuant to deferred stock unit awards (in Shares)	5,313
Forfeitures of restricted shares (in Shares)	(20,704)
Shares repurchased and retired	(19,017)	(8)	(19,009)	0	0	0
Shares repurchased and retired (in Shares)	(833,552)
Equity-based compensation expense	5,090	0	5,090	0	0	0
Currency translation adjustment and derivative transactions, net	(11,764)	0	0	0	(11,645)	(119)
Balance at Sep. 30, 2013	$ 722,153	$ 386	$ 244,189	$ 456,319	$ 3,615	$ 17,644
Balance (in Shares) at Sep. 30, 2013	38,576,118