Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 977,025	$ 860,661	$ 794,059
Cost of sales	530,761	448,211	435,140
Gross profit	446,264	412,450	358,919
Operating expenses:
Research and development and other engineering	47,616	46,248	46,196
Selling	114,903	98,343	90,663
General and administrative	144,738	129,162	113,428
Net gain on disposal of assets	(160)	(780)	(389)
Total operating expenses	307,097	272,973	249,898
Income from operations	139,167	139,477	109,021
Loss in equity method investment, before tax	(86)	0	0
Interest income	389	570	655
Interest expense	(1,177)	(1,147)	(997)
Gain on bargain purchase of a business	(6,336)	0	0
Loss on disposal of a business	(211)	0	0
Income before taxes	144,418	138,900	108,679
Provision for income taxes	51,801	49,166	40,791
Net income	$ 92,617	$ 89,734	$ 67,888
Earnings per share of common stock:
Basic (in USD per share)	$ 1.95	$ 1.87	$ 1.39
Diluted (in USD per share)	$ 1.94	$ 1.86	$ 1.38
Weighted average number of shares of common stock outstanding
Basic (in shares)	47,486	48,084	48,952
Diluted (in shares)	47,774	48,295	49,181

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.