Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Allowance for doubtful accounts	$ 40.6	$ 46.7
Accumulated depreciation	1,186.1	1,168.3
Intangible assets, accumulated amortization	$ 416.9	$ 354.8
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	273,400,000	285,500,000
Treasury stock, shares	123,800,000	111,700,000