Notes Payable, Revolving Credit Facility, Interest and Amortization of Deferred Debt Costs - Scheduled Maturities of Debt, Including Scheduled Principal Amortization (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Balloon Payments
April 1 through December 31, 2016	$ 0
2017	14,442
2018	50,748
2019	60,794
2020	61,163
2021	11,011
Thereafter	430,930
Principal amount	629,088
Scheduled Principal Amortization
April 1 through December 31, 2016	18,607
2017	25,768
2018	25,902
2019	24,614
2020	21,892
2021	21,405
Thereafter	106,296
Principal amount	244,484
Total
April 1 through December 31, 2016	18,607
2017	40,210
2018	76,650
2019	85,408
2020	83,055
2021	32,416
Thereafter	537,226
Principal amount	873,572
Unamortized deferred debt costs	8,381	$ 8,700
Net	865,191
Debt Instrument [Line Items]
Outstanding line of credit	21,825	26,695
Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Outstanding line of credit	$ 23,000	$ 28,000