Summary Of Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary of Significant Accounting Policies [Line Items]
Cost-method investments, carrying value	$ 51.7
Cost-method investments, impairment loss	0	0	0
Interest cost capitalized	0.1	0.3	0.5
Deferred lease costs	12.8	10.2	5.1
Amortization expense	5.5	4.6	4.6
Unamortized deferred lease costs	22.9	15.6
Intangible assets, useful life	15 years
Impairment charge recognized, related to long-lived assets	29.0	6.4	5.5
Write-offs relating to long-lived assets and intangibles	23.1	0	0
Asset retirement obligation	$ 5.3	$ 7.5
Business acquistions period after closing date to determine additional adjustments	1 year
Acquired intangible assets, useful life	15 years
Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Lease term	5 years
Duration of site development projects	3 months
Business acquisitions performance target period	1 year
Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Lease term	10 years
Duration of site development projects	12 months
Business acquisitions performance target period	3 years