CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Accounts receivable - trade, allowance for doubtful accounts	$ 8.5	$ 8.2
Property and equipment, accumulated depreciation	$ 224.1	$ 213.3
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	1.0	1.0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200.0	200.0
Common stock, shares issued	104.5	104.4