Statement of Consolidated Shareholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common shares	Additional paid-in capital	Common shares subscribed, unissued	Retained earnings	Accumulated other comprehensive income (loss), net of tax	Common shares held in treasury	Common shares subscription receivable
Balance at the beginning of the year at Dec. 31, 2010	$ (3,072)					$ (3,072)
Balance at beginning of year, value at Dec. 31, 2010		21,457		0	176,800		(96,816)	0
Common shares, at beginning of year at Dec. 31, 2010		21,457,000
Share subscriptions, beginning balance, shares at Dec. 31, 2010				0				0
Balance at beginning of year, shares at Dec. 31, 2010							7,345,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares sold to employees, value			1,874				4,127
Options exercised, value			(876)				(2,190)
Subscription shares, issued, value			0				0
Stock-based compensation			833
Reclassification related to stock-based compensation			(110)		110
Common shares, subscribed, value				0				0
Common shares, subscribed, shares				0				0
Common shares, issued, value				0				0
Common shares, issued, shares				0				0
Cancellations, value				0				0
Cancellations, shares				0				0
Net income	14,065				14,065
Dividends					(2,362)
Currency translation adjustments						(509)
Net gain (loss) on interest rate contracts	568					568
Defined benefit pension plans	3,331					(3,331)
Shares purchased, value							(14,222)
Shares purchased, shares							779,000
Shares sold to employees, shares							(351,000)
Options exercised, shares							(162,000)
Subscription shares, issued, shares							0
Balance at the end of the year at Dec. 31, 2011	(6,344)					(6,344)
Balance at ending of year, value at Dec. 31, 2011	100,726	21,457	1,721	0	188,613		(104,721)	0
Common shares, at end of year at Dec. 31, 2011	21,456,880	21,457,000
Share subscriptions, ending balance, shares at Dec. 31, 2011				0				0
Balance at ending of year, shares at Dec. 31, 2011	13,846,000						7,611,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares sold to employees, value			1,742				4,390
Options exercised, value			(2,100)				(5,197)
Subscription shares, issued, value			428				1,078
Stock-based compensation			1,640
Reclassification related to stock-based compensation			0
Common shares, subscribed, value				12,563				9,732
Common shares, subscribed, shares				638,000				638,000
Common shares, issued, value				(1,508)				(517)
Common shares, issued, shares				(77,000)				(77,000)
Cancellations, value				0				0
Cancellations, shares				0				0
Net income	24,595				24,595
Dividends					(2,556)
Currency translation adjustments						561
Net gain (loss) on interest rate contracts	77					77
Defined benefit pension plans	1,409					(1,409)
Shares purchased, value							(18,103)
Shares purchased, shares	891,704						892,000
Shares sold to employees, shares	(327,442)						(327,000)
Options exercised, shares							(368,000)
Subscription shares, issued, shares							(77,000)
Balance at the end of the year at Dec. 31, 2012	(7,115)					(7,115)
Balance at ending of year, value at Dec. 31, 2012	118,106	21,457	3,431	11,055	210,652		(112,159)	(9,215)
Common shares, at end of year at Dec. 31, 2012	21,456,880	21,457,000
Share subscriptions, ending balance, shares at Dec. 31, 2012				561,000				561,000
Balance at ending of year, shares at Dec. 31, 2012	13,726,000	21,457,000					7,731,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares sold to employees, value			2,745				3,853
Options exercised, value			(2,273)				(4,776)
Subscription shares, issued, value			98				383
Stock-based compensation			1,007
Reclassification related to stock-based compensation			0		0
Common shares, subscribed, value	12,563			0				0
Common shares, subscribed, shares	637,714			0				0
Common shares, issued, value				(409)				(1,728)
Common shares, issued, shares				(21,000)				(21,000)
Cancellations, value				(179)				(145)
Cancellations, shares				(9,000)				(9,000)
Net income	22,853				22,853
Dividends					(2,530)
Currency translation adjustments						(1,864)
Net gain (loss) on interest rate contracts	0					0
Defined benefit pension plans	(4,586)					4,586
Shares purchased, value							(21,887)
Shares purchased, shares	931,078						931,000
Shares sold to employees, shares	(299,330)						(299,000)
Options exercised, shares	(297,508)						(319,000)
Subscription shares, issued, shares							(26,000)
Balance at the end of the year at Dec. 31, 2013	(4,393)					(4,393)
Balance at ending of year, value at Dec. 31, 2013	$ 131,138		$ 5,008	$ 10,467	$ 230,975		$ (125,034)	$ (7,342)
Common shares, at end of year at Dec. 31, 2013	21,456,880
Share subscriptions, ending balance, shares at Dec. 31, 2013				531,000				531,000
Balance at ending of year, shares at Dec. 31, 2013	13,439,000	21,457,000					8,018,000