Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Condensed Consolidated Balance Sheets
Receivables, allowance for doubtful accounts	$ 5,854	$ 5,322
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares issued	0	0
Common stock, shares authorized	150,000,000	150,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares issued	85,751,231	84,636,668
Treasury stock, shares	2,729,127	2,566,985