Intangible Assets and Liabilities (Narratives) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Intangible Assets Liabilities
Net amortization of intangibles	$ 9.6	$ 8.5	$ 19.1	$ 17.4
Minimum
Intangible Assets Liabilities
Finite-lived net lease intangibles, useful life	1 year
Maximum
Intangible Assets Liabilities
Finite-lived net lease intangibles, useful life	53 years
Maximum | Ground lease
Intangible Assets Liabilities
Finite-lived net lease intangibles, useful life	94 years