Consolidated Statement of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-In Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss	Treasury Stock
Balance, shares at Dec. 31, 2018			32,887					796
Balance, value at Dec. 31, 2018	$ 596,693		$ 329	$ 282,525	$ 338,995	$ 1,582	$ (7,234)	$ (17,922)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,345				6,345
Foreign currency translation adjustment	842						842
Minimum pension and post retirement benefit plan adjustments, net of taxes of $7	12						12
Stock compensation expense	2,371			2,371
Stock options exercised, shares			12
Stock options exercised	139			139
Net settlement of restricted stock units, shares			127					59
Net settlement of restricted stock units	(2,151)		$ 1	(1)				$ (2,151)
Balance, shares at Mar. 31, 2019			33,026					855
Balance, value at Mar. 31, 2019	605,833		$ 330	285,034	346,922		(6,380)	$ (20,073)
Balance, shares at Dec. 31, 2018			32,887					796
Balance, value at Dec. 31, 2018	596,693		$ 329	282,525	338,995	1,582	(7,234)	$ (17,922)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	50,734
Foreign currency translation adjustment	1,176
Balance, shares at Sep. 30, 2019			33,145					888
Balance, value at Sep. 30, 2019	657,213		$ 332	293,009	391,311		(6,022)	$ (21,417)
Balance, shares at Mar. 31, 2019			33,026					855
Balance, value at Mar. 31, 2019	605,833		$ 330	285,034	346,922		(6,380)	$ (20,073)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	19,913				19,913
Foreign currency translation adjustment	998						998
Minimum pension and post retirement benefit plan adjustments, net of taxes of $7	12						12
Stock compensation expense	3,720			3,720
Stock options exercised, shares			5
Stock options exercised	69			69
Awards of common shares (in shares)			8
Net settlement of restricted stock units, shares			62					25
Net settlement of restricted stock units	(998)		$ 1	(1)				$ (998)
Balance, shares at Jun. 30, 2019			33,101					880
Balance, value at Jun. 30, 2019	629,547		$ 331	288,822	366,835		(5,370)	$ (21,071)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	24,476				24,476
Foreign currency translation adjustment	(664)						(664)
Minimum pension and post retirement benefit plan adjustments, net of taxes of $7	12						12
Stock compensation expense	3,996			3,996
Stock options exercised, shares			16
Stock options exercised	192			192
Net settlement of restricted stock units, shares			28					8
Net settlement of restricted stock units	(346)		$ 1	(1)				$ (346)
Balance, shares at Sep. 30, 2019			33,145					888
Balance, value at Sep. 30, 2019	657,213		$ 332	293,009	391,311		(6,022)	$ (21,417)
Balance, shares at Dec. 31, 2019			33,192					906
Balance, value at Dec. 31, 2019	673,964	$ (291)	$ 332	295,582	405,668	(291)	(5,391)	$ (22,227)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	12,059				12,059
Foreign currency translation adjustment	(5,898)						(5,898)
Minimum pension and post retirement benefit plan adjustments, net of taxes of $7	18						18
Stock compensation expense	1,665			1,665
Stock options exercised, shares			3
Stock options exercised	24			24
Net settlement of restricted stock units, shares			193					80
Net settlement of restricted stock units	(4,184)		$ 2	(2)				$ (4,184)
Balance, shares at Mar. 31, 2020			33,388					986
Balance, value at Mar. 31, 2020	677,357		$ 334	297,269	417,436		(11,271)	$ (26,411)
Balance, shares at Dec. 31, 2019			33,192					906
Balance, value at Dec. 31, 2019	673,964	$ (291)	$ 332	295,582	405,668	$ (291)	(5,391)	$ (22,227)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	73,111
Foreign currency translation adjustment	(883)
Balance, shares at Sep. 30, 2020			33,519					1,024
Balance, value at Sep. 30, 2020	746,075		$ 335	302,107	478,488		(6,220)	$ (28,635)
Balance, shares at Mar. 31, 2020			33,388					986
Balance, value at Mar. 31, 2020	677,357		$ 334	297,269	417,436		(11,271)	$ (26,411)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	27,292				27,292
Foreign currency translation adjustment	2,815						2,815
Minimum pension and post retirement benefit plan adjustments, net of taxes of $7	18						18
Stock compensation expense	2,506			2,506
Stock options exercised, shares			6
Stock options exercised	54			54
Awards of common shares (in shares)			4
Net settlement of restricted stock units, shares			15					7
Net settlement of restricted stock units	(278)		$ 0	0				$ (278)
Balance, shares at Jun. 30, 2020			33,413					993
Balance, value at Jun. 30, 2020	709,764		$ 334	299,829	444,728		(8,438)	$ (26,689)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	33,760				33,760
Foreign currency translation adjustment	2,200						2,200
Minimum pension and post retirement benefit plan adjustments, net of taxes of $7	18						18
Stock compensation expense	1,980			1,980
Stock options exercised, shares			31
Stock options exercised	299			299
Net settlement of restricted stock units, shares			75					31
Net settlement of restricted stock units	(1,946)		$ 1	(1)				$ (1,946)
Balance, shares at Sep. 30, 2020			33,519					1,024
Balance, value at Sep. 30, 2020	$ 746,075		$ 335	$ 302,107	$ 478,488		$ (6,220)	$ (28,635)