Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data	Jun. 30, 2011	Dec. 31, 2010
Current assets
Allowance for doubtful accounts	$ 36,945	$ 30,112
Stockholders' equity
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000	10,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000	100,000
Common stock, shares issued	45,865	45,811
Common stock, shares outstanding	44,258	45,761
Treasury Stock, Shares	1,607	50