Consolidated Balance Sheets (Parentheticals) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 2,898	$ 5,026
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	58,593,802	56,518,417
Treasury stock, at cost	4,254,350	2,691,215