CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
CONDENSED CONSOLIDATED BALANCE SHEETS
Trade accounts receivable, allowance for doubtful accounts (in dollars)	$ 1,145	$ 977
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	175,772,173	175,772,173
Common stock, shares issued	158,160,719	157,320,070
Common stock, shares outstanding	158,160,719	157,320,070