Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets
Allowance for doubtful accounts receivable, current	$ 16.6	$ 17.0
Stockholders' equity
Treasury Stock, shares	9,400,000	9,200,000
Preferred Stock [Member]
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
Series A Junior Participating Preferred Stock [Member]
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 Member
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 Member
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
Common Stock [Member]
Stockholders' equity
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	800,000,000	800,000,000
Common Stock, shares issued	281,700,000	280,300,000
Common Stock, shares outstanding	272,300,000	271,100,000