CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Trade accounts receivable, allowance for doubtful accounts	$ 1,641	$ 2,709
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	150,000	150,000
Common stock, shares issued	88,899	88,841
Common stock, shares outstanding	88,899	88,841