Income Properties - Additional Information (Detail)											3 Months Ended			12 Months Ended
	Dec. 22, 2015 USD ($) ft² $ / shares	Nov. 20, 2015 USD ($) ft² $ / shares	Nov. 18, 2015 USD ($) a ft² Building	Sep. 30, 2015 USD ($) ft² $ / shares	Sep. 28, 2015 USD ($) ft² $ / shares	Jul. 16, 2015 USD ($) a ft²	May. 28, 2015 USD ($) a	May. 18, 2015 USD ($) a ft²	Apr. 17, 2015 USD ($) ft² Building $ / shares	Nov. 17, 2014 USD ($) ft²	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2015 USD ($) Property	Dec. 31, 2014 USD ($) Property	Dec. 31, 2013 USD ($) Property	Dec. 31, 2015 a	Dec. 31, 2015 Property	Dec. 31, 2015 ft²	Jan. 31, 2013 Property
Business Acquisition Information [Line Items]
Number of income properties acquired | Property															4	9		4		2
Total acquisition cost of property														$ 76,500,000	$ 42,200,000	$ 39,500,000
Aggregate purchase price														76,400,000
Purchase price allocated to land														17,100,000		$ 13,200,000
Acquired Finite Lived Intangible Assets and Liabilities														$ 31,600,000
Amortization allocated to intangible assets and liabilities, period														15 years 8 months 12 days	9 years 1 month 6 days	10 years 6 months
Area of a real estate property																	160		1,700,000
Mortgage loans on real estate, carrying amount of mortgages														$ 38,331,956
Number of single-tenant income properties sold | Property														6
Gain (loss) on sale of property									$ (497,000)		$ 13,000	$ (277,000)	$ (228,000)			$ 1,216,000
Acquisition of Land															$ 17,400,000
Number of income properties disposed of or qualified as assets held for sale | Property															1	5
Raleigh North Carolina
Business Acquisition Information [Line Items]
Purchase price allocated to buildings and improvements			$ 31,600,000
Area of property acquired | ft²			450,000
Number of buildings sold | Building			3
Area of a real estate property | a			40
Acquisition cost of property			$ 42,300,000
Percentage of property occupied			100.00%
Weighted average remaining lease term			9 years
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
Melbourne, Florida [Member]
Business Acquisition Information [Line Items]
Weighted average remaining lease term	10 years 3 months 18 days
Area of building sold | ft²	10,908
Proceeds from building	$ 3,200,000
Gain (loss) on sale of property	$ 785,000,000,000
Loss on sale of building per share after tax | $ / shares	$ 0.08
Vero Beach, Florida [Member]
Business Acquisition Information [Line Items]
Weighted average remaining lease term		8 years 3 months 18 days
Area of building sold | ft²		13,813
Proceeds from building		$ 5,400,000
Gain (loss) on sale of property		$ 950,000
Loss on sale of building per share after tax | $ / shares		$ 0.10
Clermont, Florida [Member]
Business Acquisition Information [Line Items]
Weighted average remaining lease term					7 years 1 month 6 days
Area of building sold | ft²					13,824
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]
Weighted average remaining lease term				5 years 1 month 6 days
Area of building sold | ft²				11,900
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]
Number of buildings sold | Building									2
Weighted average remaining lease term									8 years 8 months 12 days
Area of building sold | ft²									13,813
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
Apopka, Florida [Member] | Walgreen [Member]
Business Acquisition Information [Line Items]
Proceeds from building										$ 3,300,000
Area of discontinued operations sold property under lease | ft²										14,560
Single-Tenant Properties [Member]
Business Acquisition Information [Line Items]
Number of income properties acquired | Property															2			2
Multi-Tenant Properties [Member]
Business Acquisition Information [Line Items]
Number of income properties acquired | Property															2			2
Buildings and Improvements [Member]
Business Acquisition Information [Line Items]
Purchase price allocated to buildings and improvements														$ 78,900,000	$ 20,500,000	$ 23,400,000
Intangible Assets [Member]
Business Acquisition Information [Line Items]
Purchase price allocated to amortizable intangible assets														$ 12,100,000		$ 2,900,000
Intangible Assets and Liabilities [Member]
Business Acquisition Information [Line Items]
Purchase price allocated to amortizable intangible assets and liabilities															$ 4,300,000