Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Net sales	$ 752,148us-gaap_SalesRevenueNet	$ 705,322us-gaap_SalesRevenueNet	$ 656,231us-gaap_SalesRevenueNet
Cost of sales	410,118us-gaap_CostOfGoodsSold	391,791us-gaap_CostOfGoodsSold	373,759us-gaap_CostOfGoodsSold
Gross profit	342,030us-gaap_GrossProfit	313,531us-gaap_GrossProfit	282,472us-gaap_GrossProfit
Operating expenses:
Research and development and other engineering	39,018	36,843	35,919
Selling	92,031us-gaap_SellingAndMarketingExpense	85,102us-gaap_SellingAndMarketingExpense	82,364us-gaap_SellingAndMarketingExpense
General and administrative	111,500us-gaap_GeneralAndAdministrativeExpense	108,070us-gaap_GeneralAndAdministrativeExpense	99,968us-gaap_GeneralAndAdministrativeExpense
Impairment of goodwill	530us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss	2,346us-gaap_GoodwillImpairmentLoss
Net loss (gain) on disposal of assets	(325)us-gaap_GainLossOnDispositionOfAssets	2,038us-gaap_GainLossOnDispositionOfAssets	166us-gaap_GainLossOnDispositionOfAssets
Total operating expenses	242,754us-gaap_OperatingExpenses	232,053us-gaap_OperatingExpenses	220,763us-gaap_OperatingExpenses
Income from operations	99,276us-gaap_OperatingIncomeLoss	81,478us-gaap_OperatingIncomeLoss	61,709us-gaap_OperatingIncomeLoss
Interest income	901us-gaap_InterestIncomeOperating	987us-gaap_InterestIncomeOperating	1,005us-gaap_InterestIncomeOperating
Interest expense	(855)us-gaap_InterestExpense	(901)us-gaap_InterestExpense	(793)us-gaap_InterestExpense
Income before taxes	99,322	81,564	61,921
Provision for income taxes	35,791us-gaap_IncomeTaxExpenseBenefit	30,593us-gaap_IncomeTaxExpenseBenefit	20,003us-gaap_IncomeTaxExpenseBenefit
Net income	$ 63,531	$ 50,971	$ 41,918
Earnings per common share:
Basic (in dollars per share)	$ 1.30us-gaap_EarningsPerShareBasic	$ 1.05us-gaap_EarningsPerShareBasic	$ 0.87us-gaap_EarningsPerShareBasic
Diluted (in dollars per share)	$ 1.29us-gaap_EarningsPerShareDiluted	$ 1.05us-gaap_EarningsPerShareDiluted	$ 0.87us-gaap_EarningsPerShareDiluted
Weighted average number of shares outstanding
Basic (in shares)	48,977	48,521	48,339
Diluted (in shares)	49,194	48,673	48,412

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.