Condensed Consolidated Balance Sheets (Unaudited) (Parentheticals) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Statement Of Financial Position Parenthetical [Line Items]
Accumulated depreciation	$ 4,456.2	$ 4,025.0
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized	15,000,000	15,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Class A Common Stock [Member]
Statement Of Financial Position Parenthetical [Line Items]
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	211,380,055	254,300,000
Common stock, issued	34,352,114	128,759,772
Common stock, outstanding	34,352,114	85,839,827
Class B Common Stock [Member]
Statement Of Financial Position Parenthetical [Line Items]
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	87,008,602	87,008,602
Common stock, issued	0	0
Common stock, outstanding	0	0
No Class Common Stock [Member]
Statement Of Financial Position Parenthetical [Line Items]
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	1,000,000,000	1,000,000,000
Common stock, issued	352,541,841	352,204,571
Common stock, outstanding	338,783,128	340,166,109