Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ 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	$ 308,007	$ 263,002	$ 552,786	$ 482,869
Cost of sales	166,538	139,477	302,791	259,188
Gross profit	141,469	123,525	249,995	223,681
Operating expenses:
Research and development and other engineering	11,249	11,967	22,398	23,785
Selling	29,201	28,646	56,774	58,283
General and administrative	40,400	37,725	78,592	73,846
Net loss (gain) on disposal of assets	(125)	50	(1,309)	(1)
Total operating expenses	80,725	78,388	156,455	155,913
Income from operations	60,744	45,137	93,540	67,768
Income (loss) in equity method investment, before tax	2	(12)	(22)	(41)
Interest expense, net	(184)	(199)	(274)	(388)
Gain on bargain purchase of a business	0	0	0	8,388
Income before taxes	60,562	44,926	93,244	75,727
Provision for income taxes	16,476	16,712	23,729	24,392
Net income	$ 44,086	$ 28,214	$ 69,515	$ 51,335
Earnings per common share:
Basic (in dollars per share)	$ 0.95	$ 0.59	$ 1.50	$ 1.08
Diluted (in dollars per share)	$ 0.94	$ 0.59	$ 1.48	$ 1.07
Number of shares outstanding
Basic (in shares)	46,323	47,634	46,468	47,634
Diluted (in shares)	46,677	47,920	46,842	47,922
Cash dividends declared per common share (in dollars per share)	$ 0.220	$ 0.21	$ 0.430	$ 0.39

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use; (3) to conduct internal product testing; (4) or to provide engineering support to customers in the form of testing services or product uses, specifications or requirements.

No definition available.