Investments in real estate, net Land undergoing predevelopment and future development (Details)	Sep. 30, 2014 sqft
Real Estate Properties [Line Items]
Area of Real Estate Property	18,458,379
Near-term value-creation projects in North America (CIP) | North America [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	1,926,331
Near-term value-creation projects in North America (CIP) | Alexandria Center™ at Kendall Square
Real Estate Properties [Line Items]
Area of Real Estate Property	1,062,180
Land held for future development in North America | North America [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	3,400,000