Income Properties - Disposals (Detail)							3 Months Ended				9 Months Ended
	Sep. 30, 2016 USD ($) property $ / shares	Sep. 16, 2016 USD ($) property $ / shares	Jun. 22, 2016 USD ($) $ / shares	Apr. 22, 2016 USD ($) ft² $ / shares	Apr. 06, 2016 USD ($) $ / shares	Apr. 05, 2016 USD ($) $ / shares	Sep. 30, 2016 USD ($) property	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) property	Sep. 30, 2015 USD ($)	Sep. 30, 2016 a	Sep. 30, 2016 ft²	Sep. 30, 2016 USD ($)	Dec. 31, 2015 a
Schedule Of Business Acquisitions And Disposition [Line Items]
Write off of Deferred Debt Issuance Cost							$ 367,000
Area of a real estate property													1,581	1,500,000		148.35
Impairment Charges											$ 2,180,730	$ 510,041
Gain on Disposition of Assets							11,479,490			$ 3,763,140	$ 12,842,438	$ 3,781,329
Daytona Beach, Florida
Schedule Of Business Acquisitions And Disposition [Line Items]
Area of a real estate property | a													6			6
Altamonte Springs Florida | PNC Bank, N.A.
Schedule Of Business Acquisitions And Disposition [Line Items]
Impairment Charges								$ 942,000
Gain on Disposition of Assets	$ (922,000)						$ 20,000
Sold | 2016 Disposals
Schedule Of Business Acquisitions And Disposition [Line Items]
Sales price															$ 74,300,000
Gain (Loss) recognized									$ (134,000)
Number of disposed properties | property	19						19				19
Impairment Charges									$ 210,000
Sold | 2016 Disposals | Daytona Beach, Florida | American Signature Furniture
Schedule Of Business Acquisitions And Disposition [Line Items]
Weighted average remaining lease term						3 years 9 months 18 days
Sales price						$ 5,200,000
Gain (loss) on disposal						$ 197,000
Gain (loss) on sale of building per share after tax | $ / shares						$ 0.02
Sold | 2016 Disposals | Daytona Beach, Florida | Teledyne ODI
Schedule Of Business Acquisitions And Disposition [Line Items]
Weighted average remaining lease term				9 years 3 months 18 days
Sales price				$ 3,000,000
Gain (loss) on disposal				$ 822,000
Gain (loss) on sale of building per share after tax | $ / shares				$ 0.09
Area of building | ft²				15,360
Sold | 2016 Disposals | Sebring, Florida | CVS Pharmacy
Schedule Of Business Acquisitions And Disposition [Line Items]
Weighted average remaining lease term					3 years 1 month 6 days
Sales price					$ 2,400,000
Gain (loss) on disposal					$ (210,000)
Gain (loss) on sale of building per share after tax | $ / shares					$ (0.02)
Sold | 2016 Disposals | Lexington, North Carolina | Lowes
Schedule Of Business Acquisitions And Disposition [Line Items]
Weighted average remaining lease term			9 years 7 months 6 days
Sales price			$ 9,100,000
Gain (loss) on disposal			$ 344,000
Gain (loss) on sale of building per share after tax | $ / shares			$ 0.04
Sold | 2016 Disposals | Altamonte Springs Florida | PNC Bank, N.A.
Schedule Of Business Acquisitions And Disposition [Line Items]
Weighted average remaining lease term	3 years 1 month 6 days
Sales price															$ 3,000,000
Gain (loss) on disposal	$ (922,000)
Gain (loss) on sale of building per share after tax | $ / shares	$ (0.10)
Impairment Charges								$ 942,000
Gain on Disposition of Assets							$ 20,000
Sold | Portfolio Sale
Schedule Of Business Acquisitions And Disposition [Line Items]
Sales price		$ 51,600,000
Gain (loss) on disposal		11,400,000
Gain (Loss) recognized		$ 11,100,000
Gain (loss) on sale of building per share after tax | $ / shares		$ 1.20
Write off of Deferred Debt Issuance Cost		$ 367,000
Mortgage loan secured by properties portfolio		$ 23,100,000
Sold | Portfolio Sale | Single-tenant
Schedule Of Business Acquisitions And Disposition [Line Items]
Number of disposed properties | property		14
Sold | Portfolio Sale | Single-tenant | Bank of America
Schedule Of Business Acquisitions And Disposition [Line Items]
Number of disposed properties | property		9
Sold | Portfolio Sale | Single-tenant | Walgreens
Schedule Of Business Acquisitions And Disposition [Line Items]
Number of disposed properties | property		2