Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Trade accounts receivable, allowance for doubtful accounts	$ 1,537	$ 1,641
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	81,396	88,899
Common stock, outstanding (in shares)	81,396	88,899