Fair Value of Financial Instruments - Financial Instruments for which Estimates of Fair Value Differ from Carrying Amounts (Details) - USD ($) $ in Thousands		Sep. 30, 2016	Dec. 31, 2015
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Mortgage notes payable, net		$ 322,623	$ 545,753
Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Note receivable	[1]	3,365	0
Carrying Amount [Member] | Unsecured Notes Payable [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Unsecured notes payable		1,364,312	1,512,554
Carrying Amount [Member] | Variable Rate Debt [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Variable rate debt		326,626	326,410
Carrying Amount [Member] | Mortgages Notes Payable [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Mortgage notes payable, net		322,623	545,753
Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Note receivable, fair value	[1]	3,365	0
Fair Value [Member] | Unsecured Notes Payable [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument, fair value		1,415,520	1,529,346
Fair Value [Member] | Variable Rate Debt [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument, fair value		305,301	305,522
Fair Value [Member] | Mortgages Notes Payable [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument, fair value		$ 339,471	$ 597,377

[1] A note receivable is included in other assets on the Company’s consolidated balance sheet. The note was given to an unaffiliated third party to facilitate their acquisition and development of an industrial facility located in Pennsauken, New Jersey. The loan matures three years after the payment commencement date, which is 90 days after substantial completion of the development, and bears interest at 6.3% during year one, 7.0% during year two and 8.0% during year three. The Company evaluated its investment in the note receivable under ASC 310, Receivables and determined that the loan was provided at market terms and the Company does not participate in the residual profit of the unaffiliated third party. Accordingly, the investment was appropriately classified on the Company’s balance sheet as a note receivable. As the note was originated during the third quarter of 2016, the fair value approximates the carrying value. The inputs to originate the loan are unobservable and, as a result, are categorized as Level 3.