Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement [Abstract]
Net sales	$ 98,896	$ 95,662	$ 182,540	$ 179,158
Cost of sales	63,753	60,831	117,322	115,376
Gross margin	35,143	34,831	65,218	63,782
Selling, engineering and administration	22,961	20,610	45,983	41,871
Operating earnings	12,182	14,221	19,235	21,911
Interest expense, net	319	311	636	602
Earnings before income taxes	11,863	13,910	18,599	21,309
Provision for income taxes	3,962	5,096	6,471	7,863
Net earnings	$ 7,901	$ 8,814	$ 12,128	$ 13,446
Earnings per share:
Basic (in dollars per share)	$ 0.55	$ 0.62	$ 0.84	$ 0.94
Diluted (in dollars per share)	0.55	0.61	0.84	0.94
Dividends declared per common share (in dollars per share)	$ 0.19	$ 0.18	$ 0.38	$ 0.36
Shares used in computation of earnings per share:
Basic (in shares)	14,379,450	14,309,509	14,361,464	14,244,135
Impact of dilutive securities (in shares)	63,816	57,844	73,096	73,911
Diluted (in shares)	14,443,266	14,367,353	14,434,560	14,318,046