PARENTHETICAL DATA TO CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Current assets
Allowance for doubtful accounts	$ 19,192	$ 16,421
Stockholders' equity
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	57,135,228	57,042,803
Common stock, shares outstanding	54,497,227	54,118,501
Treasury stock, shares at cost	2,651,336	2,642,398