Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Consolidated Balance Sheets
Receivables, allowance for doubtful accounts	$ 9,840	$ 7,654
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	31,219,684	30,799,091
Treasury stock, shares	655,802	641,468