Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Accounts receivable, allowance	$ 1.7	$ 1.3
Restricted cash, current	40.0	40.0
Accumulated depreciation and amortization, property	611.5	576.3
Restricted cash, noncurrent	$ 20.5	$ 20.5
Preferred Stock [Member]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000	9,860
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Series A Junior Participating Preferred Stock [Member]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	0	140
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Class A Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000,000	1,000,000
Common stock, shares issued (in shares)	331,686	330,653
Common stock, shares outstanding (in shares)	331,686	330,653
Class B Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	3	3
Common stock, shares issued (in shares)	3	3
Common stock, shares outstanding (in shares)	3	3