CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts receivable, allowances	$ 30.2	$ 29.1
Property and equipment, accumulated depreciation	$ 328.1	$ 314.3
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, shares authorized		1,000,000,000
Treasury stock, shares	119,996,135	119,650,254
Nonvoting Common Stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	10,000,000	10,000,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0
Common Stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000,000
Common stock, shares issued	342,902,272	342,902,272