Description of Business and Principles of Interim Statements - Additional Information (Detail)	3 Months Ended	6 Months Ended		12 Months Ended
	Dec. 31, 2015 USD ($) a	Jun. 30, 2016 USD ($) ft² a State Property Billboard Loan	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) a	Feb. 18, 2016 a	Dec. 31, 2013 USD ($)	Jan. 31, 2013 Property
Description of Business [Line Items]
Number of states in which entity operates | State		10
Number of owned and managed commercial real estate properties | Property		37
Commercial real estate properties | Property		29
Self developed multi-tenant properties | Property		8
Gross leasable space	148.35	1,500,000		148.35	0.37
Land portfolio | a		10,500
Number of billboards leased for property | Billboard		20
Cash and cash equivalents maximum original maturity period		90 days
Restricted Cash	$ 14,060,523	$ 10,568,618		$ 14,060,523
Cash held in reserve for property taxes and insurance escrows		9,100,000
Cash held in escrow related to land transaction		306,000				$ 17,000
Number of income properties acquired | Property							2
Reserve for future interest payment		504,000
Impairment charge other-than-temporary impairments	60,000	0	$ 0	60,000
Net realized loss on investments		(575,567)	$ 130,791
Allowance for doubtful accounts	0	0		0
Amount reclassified from other assets to long-term debt	1,700,000			1,700,000
Tenant Reimbursable Expenses
Description of Business [Line Items]
Accounts receivable included in other assets	831,000	494,000		831,000
Real Estate Operations
Description of Business [Line Items]
Accounts receivable included in other assets	1,300,000	3,400,000		1,300,000
ship And Event Receivables
Description of Business [Line Items]
Accounts receivable included in other assets	$ 253,000	$ 294,000		$ 253,000
Atlanta, GA [Member]
Description of Business [Line Items]
Number of commercial mortgage loan investments | Loan		3
Katy, Texas [Member] | Reserve for Tenant Improvements [Member]
Description of Business [Line Items]
Restricted Cash		$ 634,000