Income Properties - Additional Information (Detail)		3 Months Ended		9 Months Ended
	Sep. 16, 2016 USD ($) property	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2016 USD ($) property	Sep. 30, 2015 USD ($) property
Schedule Of Business Acquisitions And Disposition [Line Items]
Number of income properties acquired | property					3
Total acquisition cost of property				$ 49,800,000	$ 34,200,000
Land acquired				20,900,000
Buildings and improvements acquired				14,600,000
Intangible assets acquired				15,100,000
Intangible liabilities assumed				$ 800,000
Amortization allocated to intangible assets and liabilities, period				17 years 2 months 12 days
Impairment Charges				$ 2,180,730	$ 510,041
Single-tenant
Schedule Of Business Acquisitions And Disposition [Line Items]
Number of income properties acquired | property				7	1
Multi-tenant
Schedule Of Business Acquisitions And Disposition [Line Items]
Number of income properties acquired | property				1	1
2016 Disposals | Sold
Schedule Of Business Acquisitions And Disposition [Line Items]
Number of disposed properties | property				19
Sales price				$ 74,300,000
Impairment Charges		$ 210,000
Portfolio Sale | Sold
Schedule Of Business Acquisitions And Disposition [Line Items]
Sales price	$ 51,600,000
Gain (loss) on disposal	$ 11,400,000
Portfolio Sale | Sold | Single-tenant
Schedule Of Business Acquisitions And Disposition [Line Items]
Number of disposed properties | property	14
2015 Disposals | Sold
Schedule Of Business Acquisitions And Disposition [Line Items]
Impairment Charges			$ 510,000
2015 Disposals | Sold | Single-tenant
Schedule Of Business Acquisitions And Disposition [Line Items]
Number of disposed properties | property					4
Sales price					$ 15,800,000
Gain (loss) on disposal					$ 3,800,000
Impairment Charges			$ 510,000