Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Allowance for doubtful accounts	$ 35.9	$ 40.6
Accumulated depreciation	1,234.8	1,186.1
Intangible assets, accumulated amortization	$ 498.0	$ 416.9
Preferred stock, par value	$ 1.00	$ 1.00
Preferred stock, shares authorized	7,500,000	7,500,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.15	$ 0.15
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	397,200,000	397,200,000
Common stock, shares outstanding	262,000,000	273,400,000
Treasury stock, shares	135,200,000	123,800,000