Intangible Assets and Liabilities - Additional Information (Detail)	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($) Property	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) Property	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) Property	Dec. 31, 2014 USD ($) Property	Dec. 31, 2013 USD ($) Property	Nov. 18, 2015 USD ($)	Jan. 31, 2013 Property
Intangible Assets And Liabilities [Line Items]
Number of income properties acquired | Property	4				4				4	4	9		2
Increase in below market value									$ 31,600,000
Lease value decreased									$ 526,000
Number of sale of income properties | Property									6
Amortization expense of intangible assets									$ 1,500,000
Net increase in Intangible in-place lease value									21,500,000
Intangible Lease Liabilities - Net	$ 31,979,559				$ 669,693				31,979,559	$ 669,693
Amortization expense of intangible assets and liabilities									1,500,000	768,000	$ 673,000
Total amortization expense									1,700,000
Income Properties	$ 5,614,294	$ 5,034,090	$ 4,132,052	$ 4,260,675	$ 4,148,526	$ 3,864,632	$ 3,552,130	$ 3,404,359	$ 19,041,111	$ 14,969,647	$ 12,828,214
Weighted Average Maturity [Member]
Intangible Assets And Liabilities [Line Items]
Amortization period of intangible assets and liabilities									20 years
Income Properties Revenue [Member]
Intangible Assets And Liabilities [Line Items]
Income Properties									$ 200,000
Wells Fargo, Raleigh, NC [Member]
Intangible Assets And Liabilities [Line Items]
Intangible Lease Liabilities - Net												$ 31,600,000
Value of In-Place Leases, Net [Member]
Intangible Assets And Liabilities [Line Items]
Increase in sub total intangible lease assets									$ 8,100,000
Number of income properties acquired | Property	3								3
Value of Above Market In-Place Leases, Net [Member]
Intangible Assets And Liabilities [Line Items]
Increase in sub total intangible lease assets									$ 1,100,000
Value of Intangible Leasing Costs, Net [Member]
Intangible Assets And Liabilities [Line Items]
Increase in sub total intangible lease assets									$ 2,900,000