Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net sales	$ 113,648	$ 104,176	$ 218,689	$ 205,782
Cost of sales	72,144	63,122	140,437	126,078
Gross margin	41,504	41,054	78,252	79,704
Selling, engineering and administration	25,153	24,214	51,927	49,299
Operating earnings	16,351	16,840	26,325	30,405
Interest expense, net	409	147	699	325
Other pension and postretirement costs	8,031	249	8,012	345
Earnings before income taxes	7,911	16,444	17,614	29,735
Provision for income taxes	1,757	5,830	3,914	10,372
Net earnings	$ 6,154	$ 10,614	$ 13,700	$ 19,363
Earnings per share:
Basic (in dollars per share)	$ 0.21	$ 0.37	$ 0.47	$ 0.67
Diluted (in dollars per share)	0.21	0.36	0.47	0.67
Dividends declared per common share (in dollars per share)	$ 0.130	$ 0.115	$ 0.260	$ 0.23
Shares used in computation of earnings per share:
Basic (in shares)	28,963,373	28,938,451	28,965,735	28,938,851
Impact of dilutive securities (in shares)	170,070	159,369	193,665	170,824
Diluted (in shares)	29,133,443	29,097,820	29,159,400	29,109,675