Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Sep. 30, 2011	Dec. 31, 2010
Condensed Consolidated Balance Sheets
Allowances for doubtful accounts	$ 3,527	$ 2,588
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	95,000,000	95,000,000
Common stock, shares issued	55,348,571	53,700,629
Common stock, shares outstanding	46,668,003	45,020,061
Treasury stock, shares	8,680,568	8,680,568