Organization and Description of Business (Narrative) (Details) $ in Millions		6 Months Ended
	Jun. 08, 2017	Jun. 30, 2017 USD ($) property
Organization and Description of Business [Line Items]
Number of properties		145
Merger agreement, common stock, conversion ratio	0.545
Merger agreement, common unit, conversion ratio	0.545
Merger agreement, preferred stock, conversion ratio	1
Merger agreement, termination fee | $		$ 300.0
DFT
Organization and Description of Business [Line Items]
Merger agreement, termination fee | $		$ 150.0
Series C preferred stock
Organization and Description of Business [Line Items]
Preferred Stock, dividend rate	6.625%
Common Interest
Organization and Description of Business [Line Items]
Ownership percentage in the Operating Partnership		98.50%
Preferred Interest
Organization and Description of Business [Line Items]
Ownership percentage in the Operating Partnership		100.00%
United States
Organization and Description of Business [Line Items]
Number of properties		104
Europe
Organization and Description of Business [Line Items]
Number of properties		32
Asia
Organization and Description of Business [Line Items]
Number of properties		4
Australia
Organization and Description of Business [Line Items]
Number of properties		3
Canada
Organization and Description of Business [Line Items]
Number of properties		2
Unconsolidated Properties
Organization and Description of Business [Line Items]
Number of properties		14
Held-for-sale
Organization and Description of Business [Line Items]
Number of properties		5