Consolidated Statement of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Balance, shares at Dec. 31, 2017		32,332				615
Balance, value at Dec. 31, 2017	$ 531,719	$ 323	$ 271,957	$ 274,562	$ (4,366)	$ (10,757)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	8,352
Foreign currency translation adjustment	110				110
Minimum pension and post retirement benefit plan adjustments, net of taxes of $4	27				27
Stock compensation expense	2,097		2,097
Stock options exercised, shares		13
Stock options exercised	226	$ 0	226
Net settlement of restricted stock units, shares		53				24
Net settlement of restricted stock units	(850)	$ 1	(1)			$ (850)
Balance, shares at Mar. 31, 2018		32,398				639
Balance, value at Mar. 31, 2018	541,955	$ 324	274,279	283,538	(4,579)	$ (11,607)
Balance, shares at Dec. 31, 2018		32,887				796
Balance, value at Dec. 31, 2018	596,693	$ 329	282,525	338,995	(7,234)	$ (17,922)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,345
Foreign currency translation adjustment	842				842
Minimum pension and post retirement benefit plan adjustments, net of taxes of $4	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)