Organization of The Parent Company and The Operating Partnership (Textual) (Details)	9 Months Ended
	Sep. 30, 2018 ft² a property Parcel
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	93
Net Rentable Square Feet	16,462,764
Development Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	2
Redevelopment Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	5
Parent Company [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	99.20%
Undeveloped Parcels of Land | a	234
Undeveloped Land Held for Sale | a	37.9
Area of Additional Undeveloped Parcels of Land With Option to Purchase | a	55.5
Total Potential Development Capacity	14,200,000
Parent Company [Member] | Land Parcel One [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company [Member] | Land Parcel Two [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company [Member] | Assets Held-for-sale [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Total Potential Development Capacity	400,000
Parent Company [Member] | Leashold Interest Land [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Parcels | Parcel	2
Undeveloped Parcels of Land Held | a	1.8
Wholly-owned Management Company Subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet	25,300,000
Wholly-owned Management Company Subsidiaries [Member] | Wholly Owned Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet	16,500,000
Wholly-owned Management Company Subsidiaries [Member] | Partially Owned Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet	8,800,000