Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
Oct. 31, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net sales		$ 262,510	$ 309,932	$ 304,853	$ 259,244	$ 241,845	$ 284,178	$ 308,007	$ 244,780	$ 1,136,539	$ 1,078,809	$ 977,025
Cost of sales		152,457	172,288	170,674	148,990	143,641	150,282	167,442	137,157	644,409	598,522	533,644
Gross profit		110,053	137,644	134,179	110,254	98,204	133,896	140,565	107,623	492,130	480,287	443,381
Research and development and other engineering		11,771	11,972	11,055	12,260	10,216	10,441	11,249	11,150	47,058	43,056	47,616
Selling		28,097	27,672	28,687	28,112	26,278	26,879	29,201	27,573	112,568	109,931	114,903
General and administrative		39,333	37,047	41,345	39,549	45,004	37,358	38,807	37,399	157,274	158,568	142,749
Total operating expenses		79,201	76,691	81,087	79,921	81,498	74,678	79,257	76,122	316,900	311,555	305,268
Net gain on disposal of assets		5,759	14	561	(310)	8,810	460	125	1,184	6,024	10,579	160
Impairment of goodwill		0	0	0	0	6,686	0	0	0	0	6,686	0
Income from operations		36,611	60,967	53,653	30,023	18,830	59,678	61,433	32,685	181,254	172,625	138,273
Interest income (expense), net and other		594	711	260	172	250	88	182	114
Foreign exchange gain (loss), net		91	(1,067)	407	(591)	(530)	1,244	(689)	112	(1,160)	137	894
Loss on disposal of a business	$ (200)									0	0	(211)
Income before taxes		36,108	59,189	53,800	29,260	18,050	60,834	60,562	32,683	178,357	172,128	144,418
Provision for income taxes		8,051	15,503	14,223	6,598	5,293	16,473	16,476	7,253	44,375	45,495	51,801
Net income		$ 28,057	$ 43,686	$ 39,577	$ 22,662	$ 12,757	$ 44,361	$ 44,086	$ 25,430	$ 133,982	$ 126,633	$ 92,617
Earnings per share of common stock:
Basic		$ 0.63	$ 0.98	$ 0.89	$ 0.50	$ 0.28	$ 0.96	$ 0.95	$ 0.55	$ 3.00	$ 2.74	$ 1.95
Diluted		0.63	0.97	0.88	0.50	0.28	0.95	0.94	0.54	2.98	2.72	1.94
Cash dividends declared per share of common stock		$ 0.23	$ 0.23	$ 0.23	$ 0.22	$ 0.22	$ 0.22	$ 0.22	$ 0.21	$ 0.91	$ 0.87	$ 0.81

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.