Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Trade accounts receivable,allowance for doubtful accounts	$ 1,543	$ 1,641
Common stock, par value	$ 0.01	$ 0.01
Common stock, issued	81,365	88,899
Common stock, outstanding	81,365	88,899