CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Trade accounts receivable, allowances	$ 5,934	$ 6,225
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	87,519,715	87,302,355
Common stock, shares outstanding	69,883,808	69,875,873
Treasury stock, shares	17,635,907	17,426,482