Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Consolidated Balance Sheets [Abstract]
Trade accounts receivable, allowance for doubtful accounts	$ 5,814	$ 5,647
Preferred stock, shares authorized	5,000,000	5,000,000
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	296,071,374	295,258,674
Common stock, shares outstanding	296,071,374	295,258,674