Unaudited Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data	Sep. 30, 2011	Dec. 31, 2010
Statement of Financial Position [Abstract]
PROPERTY AND EQUIPMENT, accumulated depreciation	$ 738.1	$ 689.6
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,500,000,000	1,500,000,000
Common stock, shares issued	163,562,149	163,562,149
Treasury stock, shares	22,121,886	15,197,680