Property and Equipment (Including Concession Assets) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property and equipment (including concession assets), gross	$ 7,321.4	$ 7,281.4
Accumulated depreciation and amortization	1,575.7	1,596.6
Property and equipment (including concession assets), net	5,745.7	5,684.8
Accumulated amortization	424.9	413.3
Concession assets, net of accumulated amortization	1,923.1	1,916.5
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment (including concession assets), gross	209.3	208.9
Concession land rights [Member]
Property, Plant and Equipment [Line Items]
Property and equipment (including concession assets), gross	141.2	141.2
Road property [Member]
Property, Plant and Equipment [Line Items]
Property and equipment (including concession assets), gross	5,652.0	5,664.4
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment (including concession assets), gross	978.7	962.6
Technology and other [Member]
Property, Plant and Equipment [Line Items]
Property and equipment (including concession assets), gross	147.9	148.1
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment (including concession assets), gross	$ 192.3	$ 156.2