Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 184,764	$ 216,139	$ 216,665	$ 176,491	$ 166,630	$ 209,320	$ 207,893	$ 168,305	$ 794,059	$ 752,148	$ 705,322
Cost of sales	102,002	115,798	118,347	98,993	93,833	113,767	111,993	90,525	435,140	410,118	391,791
Gross profit	82,762	100,341	98,318	77,498	72,797	95,553	95,900	77,780	358,919	342,030	313,531
Research and development and other engineering	11,548	13,935	10,517	10,197	9,513	9,711	10,094	9,700	46,196	39,018	36,843
Selling	22,508	22,535	23,013	22,607	22,407	23,592	24,213	21,819	90,663	92,031	85,102
General and administrative	26,553	28,648	29,794	$ 28,433	25,508	29,557	29,494	26,941	113,428	111,500	108,070
Impairment of goodwill	0	0	0		38	492	0	0	0	530	0
Gain (loss) on sale of assets	(332)	(26)	(15)	$ (16)	11	(17)	(34)	(285)	(389)	(325)	2,038
Income from operations	22,485	35,249	35,009	16,277	15,320	32,218	32,133	19,605	109,021	99,276	81,478
Interest income, net	(77)	(175)	(54)	(35)	2	(27)	(15)	86
Income before taxes	22,408	35,074	34,955	16,242	15,322	32,191	32,118	19,691	108,679	99,322	81,564
Provision for (benefit from) income taxes	7,675	13,479	13,446	6,191	4,942	11,577	11,667	7,605	40,791	35,791	30,593
Net income	$ 14,733	$ 21,595	$ 21,509	$ 10,051	$ 10,380	$ 20,614	$ 20,451	$ 12,086	$ 67,888	$ 63,531	$ 50,971
Earnings per common share:
Basic (in USD per share)	$ 0.30	$ 0.44	$ 0.44	$ 0.20	$ 0.21	$ 0.42	$ 0.42	$ 0.25	$ 1.39	$ 1.30	$ 1.05
Diluted (in USD per share)	0.30	0.44	0.43	0.20	0.21	0.42	0.42	0.25	1.38	1.29	1.05
Cash dividends declared per common share (in dollars per share)	$ 0.160	$ 0.160	$ 0.160	$ 0.140	$ 0.14	$ 0.140	$ 0.140	$ 0.125	$ 0.62	$ 0.545	$ 0.375