Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Trade accounts receivable, allowance for doubtful accounts	$ 5,647	$ 4,761
Preferred stock, shares authorized	5,000,000	5,000,000
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	295,258,674	294,861,424
Common stock, shares outstanding	295,258,674	294,861,424