CONDENSED CONSOLIDATED STATEMENTS OF INCOME (LOSS) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Net sales	$ 165,051us-gaap_SalesRevenueNet	$ 146,640us-gaap_SalesRevenueNet
Cost of sales	102,696us-gaap_CostOfGoodsSold	92,721us-gaap_CostOfGoodsSold
Gross margin	62,355us-gaap_GrossProfit	53,919us-gaap_GrossProfit
Selling and administrative expenses	36,147	27,599
Research and development expenses	6,108us-gaap_ResearchAndDevelopmentExpense	4,863us-gaap_ResearchAndDevelopmentExpense
Operating income	20,100us-gaap_OperatingIncomeLoss	21,457us-gaap_OperatingIncomeLoss
Equity income in unconsolidated joint ventures	919	977
Other income (expense), net	(129)us-gaap_OtherNonoperatingIncomeExpense	(1,191)us-gaap_OtherNonoperatingIncomeExpense
Interest income (expense), net	(1,006)	(748)
Income before income tax expense	19,884	20,495
Income tax expense	6,257us-gaap_IncomeTaxExpenseBenefit	5,915us-gaap_IncomeTaxExpenseBenefit
Net income (loss)	$ 13,627us-gaap_NetIncomeLoss	$ 14,580us-gaap_NetIncomeLoss
Basic earnings per share (in dollars per share)	$ 0.74us-gaap_EarningsPerShareBasic	$ 0.81us-gaap_EarningsPerShareBasic
Diluted earnings per share (in dollars per share)	$ 0.72us-gaap_EarningsPerShareDiluted	$ 0.79us-gaap_EarningsPerShareDiluted
Shares used in computing:
Basic net income per share (shares)	18,475,507	17,950,843
Diluted net income per share (shares)	18,949,594	18,549,458

Total costs related to goods produced and sold during the reporting period.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The net amount of nonoperating interest income (expense).

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The net result for the period of deducting operating expenses from operating revenues.

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The net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items.

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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; or (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.

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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