Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Trade accounts receivable,allowance for doubtful accounts	$ 1,553	$ 1,641
Common stock, par value	$ 0.01	$ 0.01
Common stock, issued	88,081	88,899
Common stock, outstanding	88,081	88,899