Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 200,192	$ 230,974	$ 229,973	$ 199,523	$ 184,764	$ 216,139	$ 216,665	$ 176,491	$ 860,661	$ 794,059	$ 752,148
Cost of sales	105,226	117,499	118,486	107,000	102,002	115,798	118,347	98,993	448,211	435,140	410,118
Gross profit	94,966	113,475	111,487	92,523	82,762	100,341	98,318	77,498	412,450	358,919	342,030
Research and development and other engineering	12,441	10,932	11,452	11,423	11,548	13,935	10,517	10,197	46,248	46,196	39,018
Selling	24,030	24,304	24,822	25,187	22,508	22,535	23,013	22,607	98,343	90,663	92,031
General and administrative	32,376	32,543	34,945	29,298	26,553	28,648	29,794	28,433	129,162	113,428	111,500
Impairment of goodwill	0	0	0	0	0	0	0	0	0	0	530
Gain (loss) on sale of assets	(17)	(81)	(656)	(26)	(332)	(26)	(15)	(16)	(780)	(389)	(325)
Income from operations	26,136	45,777	40,924	26,641	22,485	35,249	35,009	16,277	139,477	109,021	99,276
Interest income, net	(177)	(82)	(83)	(235)	(77)	(175)	(54)	(35)
Income before taxes	25,959	45,695	40,841	26,406	22,408	35,074	34,955	16,242	138,900	108,679	99,322
Provision for (benefit from) income taxes	8,565	15,898	14,640	10,063	7,675	13,479	13,446	6,191	49,166	40,791	35,791
Net income	$ 17,394	$ 29,797	$ 26,201	$ 16,343	$ 14,733	$ 21,595	$ 21,509	$ 10,051	$ 89,734	$ 67,888	$ 63,531
Earnings per common share:
Basic (in USD per share)	$ 0.37	$ 0.62	$ 0.54	$ 0.34	$ 0.30	$ 0.44	$ 0.44	$ 0.20	$ 1.87	$ 1.39	$ 1.30
Diluted (in USD per share)	0.36	0.62	0.54	0.34	0.30	0.44	0.43	0.20	1.86	1.38	1.29
Cash dividends declared per common share (in dollars per share)	$ 0.18	$ 0.18	$ 0.18	$ 0.160	$ 0.160	$ 0.160	$ 0.160	$ 0.140	$ 0.70	$ 0.62	$ 0.545

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.