CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED BALANCE SHEETS
Trade accounts receivable, allowances (in dollars)	$ 21,692	$ 13,772
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares	125,000	125,000
Common stock, issued shares	38,692	38,581
Common stock, outstanding shares	38,692	38,581