Selected Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Selected Quarterly Financial Data (Unaudited)
Net sales	$ 160,322	$ 195,877	$ 195,596	$ 154,535	$ 144,686	$ 172,113	$ 181,703	$ 158,734	$ 706,329	$ 657,236	$ 603,446
Cost of sales	90,331	105,724	106,176	89,561	89,482	96,390	98,557	89,329	391,791	373,759	332,642
Gross profit	69,991	90,153	89,420	64,974	55,204	75,723	83,146	69,405	314,538	283,477	270,804
Research and development and other engineering	9,825	9,226	9,484	8,308	8,763	8,916	9,043	9,198	36,843	35,919	25,886
Selling	21,448	20,630	21,652	21,371	21,109	20,941	19,881	20,432	85,102	82,364	73,568
General and administrative	25,411	28,781	28,595	26,290	23,799	23,843	27,087	26,244	109,077	100,973	95,820
Impairment of Goodwill					2,346					2,346	1,282
Loss (gain) on sale of assets	1,404	631	11	(8)	124	33	(13)	23	2,038	166	191
Income from operations	11,903	30,885	29,678	9,013	(937)	21,990	27,148	13,508	81,478	61,709	74,057
Interest income, net	54	(9)	1	38	35	55	58	65
Income before taxes	11,957	30,876	29,679	9,051	(902)	22,045	27,206	13,573	81,564	61,921	78,786
Provision for (benefit from) income taxes	4,289	10,870	11,177	4,256	(6,785)	9,069	11,347	6,372	30,593	20,003	27,886
Net income	$ 7,668	$ 20,006	$ 18,502	$ 4,795	$ 5,883	$ 12,976	$ 15,859	$ 7,201	$ 50,971	$ 41,918	$ 50,900
Earnings per common share:
Basic (in dollars per share)	$ 0.16	$ 0.41	$ 0.38	$ 0.10	$ 0.12	$ 0.27	$ 0.33	$ 0.15	$ 1.05	$ 0.87	$ 1.04
Diluted (in dollars per share)	$ 0.16	$ 0.41	$ 0.38	$ 0.10	$ 0.12	$ 0.27	$ 0.33	$ 0.15	$ 1.05	$ 0.87	$ 1.04
Cash dividends declared per common share (in dollars per share)	$ 0.125	$ 0.125	$ 0.125		$ 0.25	$ 0.125	$ 0.125	$ 0.125	$ 0.375	$ 0.625	$ 0.50

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.