Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets:
Trade accounts receivable, allowances for doubtful accounts	$ 6,800	$ 2,485
Other assets:
Patents, trademarks, and other intangible assets, accumulated amortization	$ 48,951	$ 39,754
Equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	82,976,740	82,322,876
Treasury stock, shares held	2,732,259	2,672,930