Property and Equipment (including Concession Assets) (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Accumulated amortization	$ 483.1	$ 444.1
Concession assets, net of accumulated amortization	2,007.6us-gaap_FiniteLivedIntangibleAssetsNet	1,951.0us-gaap_FiniteLivedIntangibleAssetsNet
Capitalized interest during period	0.9us-gaap_InterestCostsCapitalized	1.1us-gaap_InterestCostsCapitalized	0.9us-gaap_InterestCostsCapitalized
Depreciation and amortization	$ 258.1us-gaap_DepreciationAndAmortization	$ 223.3us-gaap_DepreciationAndAmortization	$ 198.8us-gaap_DepreciationAndAmortization

The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Amount of interest capitalized during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Allowance for Funds Used during Construction

-URI http://asc.fasb.org/extlink&oid=6504829

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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