Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Trade accounts receivable, allowances for doubtful accounts	$ 2,374	$ 2,485
Other assets:
Patents, trademarks, and other intangible assets, accumulated amortization	$ 42,344	$ 39,754
Equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000us-gaap_CommonStockSharesAuthorized	100,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued	82,322,876us-gaap_CommonStockSharesIssued	82,322,876us-gaap_CommonStockSharesIssued
Treasury stock, shares held	2,689,533us-gaap_TreasuryStockShares	2,672,930us-gaap_TreasuryStockShares

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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