Organization of The Parent Company and The Operating Partnership (Textual) (Details)	Mar. 31, 2018 ft² a property
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	94
Net Rentable Square Feet	16,501,024
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	4
Parent Company [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	99.20%
Net Rentable Square Feet	8,800,000
Undeveloped Parcels of Land | a	200
Area of Additional Undeveloped Parcels of Land With Option to Purchase | a	59
Total Potential Development Capacity	14,700,000
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