Income Properties - Additional Information (Detail)							3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) ft² a Property $ / shares	Sep. 28, 2015 USD ($) ft² $ / shares	Jul. 16, 2015 USD ($) ft² a	May. 28, 2015 USD ($) a	May. 18, 2015 USD ($) ft² a	Apr. 17, 2015 USD ($) ft² Building $ / shares	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2015 USD ($) ft² a Property	Sep. 30, 2014 USD ($) Property	Dec. 31, 2014 USD ($) Property	Jan. 31, 2013 Property
Business Acquisition Information [Line Items]
Number of income properties acquired | Property	3								3		3	2
Aggregate acquisition cost of property									$ 34,200,000	$ 20,000,000
Purchase price allocated to land									8,500,000
Purchase price allocated to amortizable intangible assets									$ 6,013,622	$ 1,069,145
Amortization allocated to intangible assets, period									7 years 7 months 6 days	10 years 3 months 18 days
Area of a real estate property | ft²	1,270,000								1,270,000
Acquisition cost of property									$ 29,736,375	$ 20,815,135
Reclassifications to the purchase price allocations, increase in intangible assets											$ 3,000,000
Reclassifications to the purchase price allocations, decrease in properties, land, buildings, and improvements											(2,300,000)
Reclassifications to the purchase price allocations, increase in accrued and other liabilities											670,000
Number of single-tenant income properties sold | Property									4
Gain (loss) on sale of property						$ (497,000)	$ 13,000	$ (277,000)		(228,000)
Tenant improvements	$ 1,200,000								$ 1,200,000
Acquisition of Land									$ 5,664,787	11,600,000
Number of self-developed properties | Property	8								8
Independent Third-Party [Member]
Business Acquisition Information [Line Items]
Acquisition cost of property											$ 39,100,000
Minimum [Member]
Business Acquisition Information [Line Items]
Number of income properties acquired | Property	3								3
Maximum [Member]
Business Acquisition Information [Line Items]
Number of income properties acquired | Property	4								4
Jacksonville, Florida [Member]
Business Acquisition Information [Line Items]
Area of property acquired | ft²			136,856
Area of a real estate property | a			3.4
Acquisition cost of property			$ 25,100,000
Percentage of property occupied			99.00%
Winter Park, Florida [Member]
Business Acquisition Information [Line Items]
Area of a real estate property | a				0.71
Acquisition cost of property				$ 409,000
Glendale, Arizona [Member]
Business Acquisition Information [Line Items]
Area of property acquired | ft²					23,329
Area of a real estate property | a					2.46
Acquisition cost of property					$ 8,600,000
Initial lease term					15 years
Operating lease rent increment term, in years					5 years
Mortgage loans on real estate, carrying amount of mortgages					$ 6,200,000
Mortgage loans on real estate, maturity date					Nov. 30, 2015
Clermont, Florida [Member]
Business Acquisition Information [Line Items]
Area of building sold | ft²		13,824
Weighted average remaining lease term		7 years 1 month 6 days
Proceeds from building		$ 4,200,000
Gain (loss) on sale of property		$ 1,600,000
Loss on sale of building per share after tax | $ / shares		$ 0.17
Sanford, Florida [Member]
Business Acquisition Information [Line Items]
Area of building sold | ft²	11,900								11,900
Weighted average remaining lease term	5 years 1 month 6 days
Proceeds from building	$ 5,200,000
Gain (loss) on sale of property	$ 2,200,000
Loss on sale of building per share after tax | $ / shares	$ 0.23
Sanford and Sebastian, Florida [Member]
Business Acquisition Information [Line Items]
Area of building sold | ft²						13,813
Weighted average remaining lease term						8 years 8 months 12 days
Proceeds from building						$ 6,400,000
Gain (loss) on sale of property						$ (497,000)
Loss on sale of building per share after tax | $ / shares						$ 0.05
Number of buildings sold | Building						2
Teledyne ODI [Member]
Business Acquisition Information [Line Items]
Area of leased property | ft²									15,000
Expanded and Extended State of Florida Department of Revenue [Member]
Business Acquisition Information [Line Items]
Area of leased property | ft²									21,000
Daytona Beach, Florida [Member]
Business Acquisition Information [Line Items]
Area of a real estate property | a	6								6
Cost related to construction										$ 2,400,000
Single-Tenant Properties [Member]
Business Acquisition Information [Line Items]
Number of income properties acquired | Property	1								1	2
Multi-Tenant Properties [Member]
Business Acquisition Information [Line Items]
Number of income properties acquired | Property	1								1
Multi-Tenant Properties [Member] | Daytona Beach, Florida [Member]
Business Acquisition Information [Line Items]
Number of self-developed properties | Property										2
Buildings and Improvements [Member]
Business Acquisition Information [Line Items]
Purchase price allocated to buildings and improvements									$ 19,700,000	$ 5,600,000
Buildings and Improvements [Member] | Daytona Beach, Florida [Member]
Business Acquisition Information [Line Items]
Cost related to construction										2,200,000
Land [Member] | Daytona Beach, Florida [Member]
Business Acquisition Information [Line Items]
Cost related to construction										221,000
Intangible Assets [Member]
Business Acquisition Information [Line Items]
Purchase price allocated to amortizable intangible assets									$ 6,000,000	$ 2,800,000