Parenthetical Data To The Consolidated Balance Sheets (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2011	Dec. 31, 2010
Current assets
Trade accounts receivable, allowances for doubtful accounts	$ 2,591	$ 2,590
Other assets
Patents, trademarks and other intangible assets, accumulated amortization	$ 21,512	$ 21,499
Equity
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	78,843,704	77,825,398
Treasury stock, shares held (in shares)	1,696,989	1,533,653