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, 2009	$ (4,949)					$ (4,949)
Balance at beginning of year, value at Dec. 31, 2009			328	1,204	165,293		(86,084)	(26)
Common shares, at beginning of year at Dec. 31, 2009		21,457,000
Share subscriptions, beginning balance, shares at Dec. 31, 2009				201,000				(201,000)
Balance at beginning of year, shares at Dec. 31, 2009							6,885,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares sold to employees, value			996				4,598
Options exercised, value			(1,254)				2,876
Subscription shares, issued, value			(1,303)				2,505
Stock-based compensation			1,123
Reclassification related to stock-based compensation			110		(110)
Common shares, subscribed, value				0				0
Common shares, subscribed, shares				0				0
Common shares, issued, value				(1,202)				24
Common shares, issued, shares				(200,000)				200,000
Cancellations, value				(2)				2
Cancellations, shares				(1,000)				1,000
Net income	14,053				14,053
Dividends					(2,436)
Currency translation adjustments						1,404
Net gain (loss) on interest rate contracts	195					195
Defined benefit pension plans	278					278
Shares purchased, value							(20,711)
Shares purchased, shares							1,249,000
Shares sold to employees, shares							(363,000)
Options exercised, shares							(226,000)
Subscription shares, issued, shares							(200,000)
Balance at the end of the year at Dec. 31, 2010	(3,072)					(3,072)
Balance at ending of year, value at Dec. 31, 2010	98,369	21,457	0	0	176,800		(96,816)	0
Common shares, at end of year at Dec. 31, 2010		21,457,000
Share subscriptions, ending balance, shares at Dec. 31, 2010				0				0
Balance at ending of year, shares at Dec. 31, 2010	14,112,000						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	779,838						779,000
Shares sold to employees, shares	351,285						(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	21,457,000	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	21,457,000					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		0
Common shares, subscribed, value	12,563			12,563				(9,732)
Common shares, subscribed, shares	637,714			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	341,531						(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