Property and Equipment - Summary of Property, Plant and Equipment (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
Property and Equipment [Line Items]
Property and Equipment	1,890.1us-gaap_PropertyPlantAndEquipmentGross	1,892.0us-gaap_PropertyPlantAndEquipmentGross	$ 1,879.2us-gaap_PropertyPlantAndEquipmentGross
Less: accumulated depreciation	1,185.7	1,136.6	1,071.3
Property and equipment, net	704.4us-gaap_PropertyPlantAndEquipmentNet	755.4us-gaap_PropertyPlantAndEquipmentNet	807.9us-gaap_PropertyPlantAndEquipmentNet
Land [Member]
Property and Equipment [Line Items]
Property and Equipment	88.4	88.6	87.8
Building and Improvements
Property and Equipment [Line Items]
Property and Equipment	47.5	45.0	45.7
Building and Improvements \| Minimum
Property and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	20 years	20 years
Building and Improvements \| Maximum
Property and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	40 years	40 years
Advertising Structures
Property and Equipment [Line Items]
Property and Equipment	1,662.4	1,662.3	1,655.9
Advertising Structures \| Minimum
Property and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years	5 years
Advertising Structures \| Maximum
Property and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	20 years	20 years
Furniture, Equipment and Other
Property and Equipment [Line Items]
Property and Equipment	76.1	77.2	76.3
Furniture, Equipment and Other \| Minimum
Property and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years	3 years
Furniture, Equipment and Other \| Maximum
Property and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years	10 years
Construction in progress [Member]
Property and Equipment [Line Items]
Property and Equipment	15.7	18.9	$ 13.5

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.14)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 14

-Article 5

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- Definition

Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 13

-Subparagraph a

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

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- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

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