PARENTHETICAL DATA TO CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets
Allowance for doubtful accounts	$ 22,728	$ 16,421
Stockholders' equity
Preferred stock, par value	$ 0.00	$ 0.00
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	$ 0.00	$ 0.00
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	57,800,791	57,042,803
Common stock, shares outstanding	55,109,038	54,118,501
Treasury stock, shares at cost	2,638,421	2,642,398