Investments in real estate, net Land undergoing predevelopment and future development (Details) $ in Thousands	Sep. 30, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)
Real Estate Properties [Line Items]
Land available for development | $	$ 311,932	$ 683,101
Area of Real Estate Property	19,943,739
Square Footage of Real Estate Property, Future Development	11,527,268
Near-term value-creation projects in North America (CIP)
Real Estate Properties [Line Items]
Land available for development | $	$ 47,400
Area of Real Estate Property	1,310,186
Land held for future development in North America
Real Estate Properties [Line Items]
Land available for development | $	$ 264,600
Square Footage of Real Estate Property, Future Development	10,200,000