Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Condensed Consolidated Balance Sheets [Abstract]
Trade accounts receivable, allowance for doubtful accounts	$ 2,715	$ 2,709
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares issued	89,169	88,841
Common stock, shares outstanding	89,169	88,841