Notes Payable and Unsecured Credit Facility (Schedule of Future Principal Payments Due on Notes Payable and Unsecured Credit Facility) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) extension loan
Debt Instrument [Line Items]
Nine months ending December 31, 2017	$ 182,535	[1]
2018	317,008
2019	170,647
2020	136,160
2021	1,239
Thereafter	48,763
Total	856,352
Note Payable Two [Member]
Debt Instrument [Line Items]
Nine months ending December 31, 2017	$ 105,850
Notes payable, maturity date	Aug. 21, 2017
Notes payable, extension period	2 years
Note Payable Three [Member]
Debt Instrument [Line Items]
Nine months ending December 31, 2017	$ 18,707
Notes payable, maturity date	Oct. 11, 2017
Notes payable, extension period	1 year
Notes payable, number of extension periods | extension	2
Notes Payable [Member]
Debt Instrument [Line Items]
Nine months ending December 31, 2017	$ 51,161
Number of loan agreements | loan	3

[1] Of this amount, $105,850,000 relates to one loan agreement with a maturity date of August 21, 2017, subject to the Company's right to a two-year extension and $18,707,000 relates to one loan agreement, the maturity date of which is October 11, 2017, subject to the Company's right to two one-year extensions. The Company may refinance these loan agreements or exercise the extension options depending upon refinancing terms available at the time. In addition, $51,161,000 relates to three loan agreements of which the Company may elect to add to the unencumbered pool of the unsecured credit facility.