Statements of Consolidated Shareholders' Equity - USD ($) $ in Thousands	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
Common shares, at beginning of year at Dec. 31, 2015		35,141,000
Balance at beginning of year, value at Dec. 31, 2015		$ 35,141	$ 24,340	$ 8,591	$ 123,307		$ (159,429)	$ 4,106
Increase (decrease) in stockholders' equity [Roll Forward]
Reclassifications of temporary to permanent equity, shares		716,000
Reclassifications of temporary to permanent equity, value		$ 716
Share subscriptions, beginning balance, shares at Dec. 31, 2015				(872,000)				(872,000)
Balance at beginning of year, shares at Dec. 31, 2015							17,427,000
Balance at the beginning of the year at Dec. 31, 2015	$ (13,394)					$ (13,394)
Increase (decrease) in stockholders' equity [Roll Forward]
Shares purchased, value							$ (25,290)
Shares sold to employees, value			4,182				5,298
Options exercised, value			(992)				(2,442)
Subscription shares, issued, value			(21)				$ 449
Stock-based compensation			2,860
Change in common shares related to 401KSOP and ESOP related shares					(9,043)
Adjustments to additional paid in capital, other			11,215		0
Common shares, issued, value				$ (325)				$ (1,104)
Common shares, issued, shares				(32,000)				(32,000)
Cancellations, value				$ (57)				$ (29)
Cancellations, shares				(6,000)				(6,000)
Net income	22,284				22,284
Dividends					(2,597)
Currency translation adjustments						744
Defined benefit pension plans	(488)					488
Shares purchased, shares							1,492,000
Shares sold							(617,000)
Options exercised, shares							(262,000)
Subscription shares, issued, shares							(49,000)
Balance at ending of year, value at Dec. 31, 2016	$ 27,978	$ 35,857	41,626	$ 8,209	133,951		$ (176,530)	$ 2,973
Share subscriptions, ending balance, shares at Dec. 31, 2016				(834,000)				(834,000)
Balance at ending of year, shares at Dec. 31, 2016	17,866,000						17,991,000
Balance at the end of the year at Dec. 31, 2016	$ (12,162)					(12,162)
Common shares, at end of year at Dec. 31, 2016	35,856,856	35,857,000
Increase (decrease) in stockholders' equity [Roll Forward]
Reclassifications of temporary to permanent equity, shares		590,000
Reclassifications of temporary to permanent equity, value		$ 590
Shares purchased, value							$ (30,566)
Shares sold to employees, value			5,690				5,206
Options exercised, value			76				(2,634)
Subscription shares, issued, value			(35)				$ 929
Stock-based compensation			1,220
Change in common shares related to 401KSOP and ESOP related shares					(9,885)
Adjustments to additional paid in capital, other			9,977		162
Common shares, issued, value				$ (567)				$ (1,123)
Common shares, issued, shares				(59,000)				(59,000)
Cancellations, value				$ (113)				$ (75)
Cancellations, shares				(11,000)				(11,000)
Net income	$ 22,120				22,120
Dividends					(2,513)
Currency translation adjustments						2,196
Defined benefit pension plans	$ (1,574)					1,573
Shares purchased, shares	1,697,727						1,698,000
Shares sold	(662,806)						(663,000)
Options exercised, shares							(242,000)
Subscription shares, issued, shares							(91,000)
Balance at ending of year, value at Dec. 31, 2017	$ 37,870	$ 36,447	58,554	$ 7,529	143,835		$ (198,327)	$ 1,775
Share subscriptions, ending balance, shares at Dec. 31, 2017				(764,000)				(764,000)
Balance at ending of year, shares at Dec. 31, 2017	17,754,000						18,693,000
Balance at the end of the year at Dec. 31, 2017	$ (8,393)					(8,393)
Common shares, at end of year at Dec. 31, 2017	36,446,890	36,447,000
Increase (decrease) in stockholders' equity [Roll Forward]
Reclassifications of temporary to permanent equity, shares		825,000
Reclassifications of temporary to permanent equity, value		$ 825
Shares purchased, value							$ (51,116)
Shares sold to employees, value			6,820				10,617
Options exercised, value			145				(2,326)
Subscription shares, issued, value			(99)				$ 1,458
Stock-based compensation			1,958
Change in common shares related to 401KSOP and ESOP related shares					(11,598)
Adjustments to additional paid in capital, other			15,245		(355)
Common shares, subscribed, value	$ (12,563)
Common shares, subscribed, shares	(1,275,428)
Common shares, issued, value				$ (543)				$ (1,005)
Common shares, issued, shares				(55,000)				(55,000)
Cancellations, value				$ (187)				$ (41)
Cancellations, shares				(19,000)				(19,000)
Net income	$ 27,977				27,977
Dividends					(2,387)
Currency translation adjustments						(2,514)
Defined benefit pension plans	$ (5,873)					5,873
Shares purchased, shares	2,636,943						2,637,000
Shares sold	(960,740)						(961,000)
Options exercised, shares							(207,000)
Subscription shares, issued, shares							(129,000)
Balance at ending of year, value at Dec. 31, 2018	$ 43,361	$ 37,272	$ 82,623	$ 6,799	$ 157,472		$ (235,042)	$ 729
Share subscriptions, ending balance, shares at Dec. 31, 2018				(690,000)				(690,000)
Balance at ending of year, shares at Dec. 31, 2018	17,239,000						20,033,000
Balance at the end of the year at Dec. 31, 2018	$ (5,034)					$ (5,034)
Common shares, at end of year at Dec. 31, 2018	37,271,606	37,272,000