CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Allowance for doubtful accounts on trade receivables	$ 3.5	$ 3.2
Treasury Stock, at cost, shares	754,853	671,271
Class A Common Stock [Member]
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	900,000,000	900,000,000
Common Stock, shares issued	49,986,651	49,986,651
Class B Common Stock [Member]
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	200,000,000	200,000,000
Common Stock, shares issued	3,125,000	3,125,000
Common Stock, shares outstanding	3,125,000	3,125,000
Treasury Stock [Member] | Class A Common Stock [Member]
Treasury Stock, at cost, shares	754,853	671,271