Organization and Description of Business (Narrative) (Details)	Mar. 31, 2017 property
Organization and Description of Business [Line Items]
Number of properties	145
Common Interest
Organization and Description of Business [Line Items]
Ownership percentage in the Operating Partnership	98.40%
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	3