Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data	Jun. 30, 2011	Dec. 31, 2010
Current assets
Allowance for doubtful accounts receivable, current	$ 22.7	$ 30.3
Stockholders' equity
Preferred Stock, par value	$ 0.01	$ 0.01
Preferred Stock, shares authorized	10,000,000	10,000,000
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	800,000,000	800,000,000
Common Stock, shares issued	279,981,794	279,149,028
Common Stock, shares outstanding	270,829,764	270,236,256
Treasury Stock, shares	9,152,030	8,912,772
Series A Junior Participating Preferred Stock
Stockholders' equity
Preferred Stock, par value	$ 0.01	$ 0.01
Preferred Stock, shares authorized	1,500,000	1,500,000
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Perpetual Preferred Stock
Stockholders' equity
Preferred Stock, shares authorized	800,000	800,000
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Series Common Stock
Stockholders' equity
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	40,000,000	40,000,000
Common Stock, shares issued	0	0
Common Stock, shares outstanding	0	0