Income Properties - Additional Information (Detail)			3 Months Ended
	Mar. 28, 2016 USD ($) $ / shares	Feb. 18, 2016 USD ($) ft² a	Mar. 31, 2016 USD ($) ft² Property	Mar. 31, 2015 USD ($)	Dec. 31, 2015 a	Jan. 31, 2013 Property
Business Acquisition Information [Line Items]
Number of income properties acquired | Property						2
Total acquisition cost of property			$ 2,500,000
Purchase price allocated to land			1,000,000
Purchase price allocated to amortizable intangible liabilities			$ 200,000
Amortization allocated to intangible assets and liabilities, period			8 years 3 months 18 days
Area of office building acquired | ft²		4,685
Area of a real estate property		0.37	1,700,000		160
Acquisition price of real state property		$ 2,500,000
Weighted average remaining lease term		8 years 2 months 12 days
Impairment Charges			$ 209,908	$ 510,041
Sale price of property portfolio	$ 51,600,000
Mortgage loan secured by properties portfolio	23,100,000
Estimated gain on sale of properties portfolio	$ 11,400,000		$ 134,000	$ 277,000
Loss on sale of property portfolio per share after tax | $ / shares	$ 1.22
Multi-Tenant Properties [Member]
Business Acquisition Information [Line Items]
Number of income properties acquired | Property			1
Building and Building Improvements
Business Acquisition Information [Line Items]
Purchase price allocated to buildings and improvements			$ 1,600,000
Intangible Assets [Member]
Business Acquisition Information [Line Items]
Purchase price allocated to amortizable intangible assets			$ 100,000