Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Net sales	$ 425,544	$ 424,625	$ 433,732
Cost of sales	257,295	261,097	271,383
Gross margin	168,249	163,528	162,349
Selling, engineering and administration	103,093	101,380	105,480
Operating earnings	65,156	62,148	56,869
Interest expense, net	30	253	1,157
Other pension and postretirement costs	145	288	19,860
Earnings before income taxes	64,981	61,607	35,852
Provision for income taxes	15,638	14,430	8,062
Net earnings	$ 49,343	$ 47,177	$ 27,790
Earnings per share:
Basic	$ 1.70	$ 1.63	$ 0.96
Diluted	$ 1.69	$ 1.61	$ 0.95
Shares used in computation of earnings per share:
Basic	29,052	29,028	28,993
Impact of dilutive securities	178	192	196
Diluted	29,230	29,220	29,189