Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Sep. 30, 2011	Dec. 31, 2010
Current assets:
Trade accounts receivable, allowances for doubtful accounts	$ 2,422	$ 2,590
Other assets:
Patents, trademarks and other intangible assets, accumulated amortization	$ 22,040	$ 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)	78,978,031	77,825,398
Treasury stock, shares held (in shares)	1,722,957	1,533,653