Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015
Real Estate Properties [Line Items]
Minimum Percentage of Ordinary Taxable Income Distribution Requirement				90.00%
Foreign Tax Authority [Member]
Real Estate Properties [Line Items]
Income Tax Provision, Sale of Real Estate Investment	$ 0.0			$ 0.0
Alte Jakobstrabe Berlin [Member] | Foreign Tax Authority [Member]
Real Estate Properties [Line Items]
Income Tax Provision, Sale of Real Estate Investment		$ (0.5)	$ 2.2		$ 1.7