Investments in Real Estate (Acquisitions) (Details) - USD ($) $ in Millions					12 Months Ended
	Dec. 18, 2015	Nov. 16, 2015	Jun. 25, 2015	Apr. 15, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Purchase price					$ 95.2
Deer Park 3
Business Acquisition [Line Items]
Purchase price				$ 1.6
3 Loyang Way
Business Acquisition [Line Items]
Purchase price			$ 45.0
Renewal term			28 years
Digital Loudoun III
Business Acquisition [Line Items]
Purchase price		$ 43.0
Digital Frankfurt
Business Acquisition [Line Items]
Purchase price	$ 5.6