Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Net sales	$ 263,002	$ 229,973	$ 482,869	$ 429,496
Cost of sales	139,477	118,486	259,188	225,486
Gross profit	123,525	111,487	223,681	204,010
Operating expenses:
Research and development and other engineering	13,264	11,452	26,371	22,875
Selling	28,511	24,822	57,994	50,009
General and administrative	36,563	34,945	71,549	64,243
Net loss (gain) on disposal of assets	50	(656)	(1)	(682)
Total operating expenses	78,388	70,563	155,913	136,445
Income from operations	45,137	40,924	67,768	67,565
Loss in equity method investment, before tax	(12)	0	(41)	0
Interest expense, net	(199)	(83)	(388)	(318)
Gain on bargain purchase of a business	0	0	8,388	0
Income before taxes	44,926	40,841	75,727	67,247
Provision for income taxes	16,712	14,640	24,392	24,703
Net income	$ 28,214	$ 26,201	$ 51,335	$ 42,544
Earnings per common share:
Basic (in dollars per share)	$ 0.59	$ 0.54	$ 1.08	$ 0.88
Diluted (in dollars per share)	$ 0.59	$ 0.54	$ 1.07	$ 0.88
Number of shares outstanding
Basic (in shares)	47,634	48,399	47,634	48,353
Diluted (in shares)	47,920	48,605	47,922	48,533
Cash dividends declared per common share (in dollars per share)	$ 0.21	$ 0.18	$ 0.39	$ 0.34