Statements 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, 2011	$ (6,344)					$ (6,344)
Balance at beginning of year, value at Dec. 31, 2011		(21,457)	(1,721)	0	(188,613)		104,721	0
Common shares, at beginning of year at Dec. 31, 2011		21,457,000
Share subscriptions, beginning balance, shares at Dec. 31, 2011				0				0
Balance at beginning of year, shares at Dec. 31, 2011							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
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							892,000
Shares sold to employees, shares							(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						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
Common shares, subscribed, value				0				0
Common shares, subscribed, shares				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							(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)	(21,457)	(5,008)	(10,467)	(230,975)		125,034	(7,342)
Common shares, at end of year at Dec. 31, 2013	21,456,880	21,457,000
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	21,456,880					8,018,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares sold to employees, value			3,417				3,822
Options exercised, value			(273)				(1,861)
Subscription shares, issued, value			184				794
Stock-based compensation			1,125
Common shares, subscribed, value	(12,563)			0				0
Common shares, subscribed, shares	(637,714)			0				0
Common shares, issued, value				(758)				(1,543)
Common shares, issued, shares				(39,000)				(39,000)
Cancellations, value				(328)				(199)
Cancellations, shares				(16,000)				(16,000)
Net income	23,169				23,169
Dividends					(2,674)
Currency translation adjustments						(2,798)
Net gain (loss) on interest rate contracts	0					0
Defined benefit pension plans	4,332					(4,332)
Shares purchased, value							(19,598)
Shares purchased, shares	727,436						727,000
Shares sold to employees, shares	(287,536)						(287,000)
Options exercised, shares	(74,715)						(116,000)
Subscription shares, issued, shares							(50,000)
Balance at the end of the year at Dec. 31, 2014	(11,523)					(11,523)
Balance at ending of year, value at Dec. 31, 2014	$ (136,491)	$ (21,457)	$ (9,461)	$ (9,381)	$ (251,470)		$ 138,155	$ (5,600)
Common shares, at end of year at Dec. 31, 2014	21,456,880	21,457,000
Share subscriptions, ending balance, shares at Dec. 31, 2014				(476,000)				(476,000)
Balance at ending of year, shares at Dec. 31, 2014	13,165,000	21,456,880					8,292,000