Background Schedule of rentable square feet (Details)	Sep. 30, 2016 ft²
Consolidated Properties [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	17,983,800
Total Square Footage of Asset Base	23,662,507
Consolidated Properties [Member] | Future Value-creation Projects [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property, Future Development	5,678,707
Unconsolidated Properties [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	836,779
Total Square Footage of Asset Base	836,779
Unconsolidated Properties [Member] | Future Value-creation Projects [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property, Future Development	0
North America
Real Estate Properties [Line Items]
Area of Real Estate Property	18,820,579
Total Square Footage of Asset Base	24,499,286
North America | Future Value-creation Projects [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property, Future Development	5,678,707
Operating properties [Member] | Consolidated Properties [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	16,052,751
Operating properties [Member] | Unconsolidated Properties [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	313,407
Operating properties [Member] | North America
Real Estate Properties [Line Items]
Area of Real Estate Property	16,366,158
Development and Redevelopment Projects[Member] | Consolidated Properties [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	1,931,049
Development and Redevelopment Projects[Member] | Unconsolidated Properties [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	523,372
Development and Redevelopment Projects[Member] | North America
Real Estate Properties [Line Items]
Area of Real Estate Property	2,454,421
Projects to be delivered by 4Q16 [Member] | Consolidated Properties [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	366,081
Projects to be delivered by 4Q16 [Member] | Unconsolidated Properties [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	100,392
Projects to be delivered by 4Q16 [Member] | North America
Real Estate Properties [Line Items]
Area of Real Estate Property	466,473
Projects to be delivered in 2017 and 2018 [Member] | Consolidated Properties [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	1,564,968
Projects to be delivered in 2017 and 2018 [Member] | Unconsolidated Properties [Member]
Real Estate Properties [Line Items]
Area of Real Estate Property	422,980
Projects to be delivered in 2017 and 2018 [Member] | North America
Real Estate Properties [Line Items]
Area of Real Estate Property	1,987,948