Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Current assets
Allowance for doubtful accounts	$ 5.8	$ 7.4
Stockholders' equity
Treasury Stock, shares	13,900,000	13,800,000
Preferred Stock [Member]
Stockholders' equity
Preferred Stock, par value per share	$ 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
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 per share	$ 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 per share	$ 0.01	$ 0.01
Common Stock, shares authorized	800,000,000	800,000,000
Common Stock, shares issued	285,400,000	283,900,000
Common Stock, shares outstanding	271,500,000	270,100,000