Intangible Assets and Liabilities (Narratives) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Intangible Assets Liabilities
Net amortization of intangibles	$ 9.1	$ 9.4
Minimum
Intangible Assets Liabilities
Finite-lived net lease intangibles, useful life	3 years
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