Investments in real estate, net Development and redevelopment projects (Details)	Sep. 30, 2014 sqft
Real Estate Properties [Line Items]
Area of Real Estate Property	18,458,379
Development [Member]
Real Estate Properties [Line Items]
Number of real estate properties	7
Redevelopment [Member]
Real Estate Properties [Line Items]
Number of real estate properties	2
North America [Member] | Development [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	1,636,424
North America [Member] | Redevelopment [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	143,777