INCOME PROPERTIES - Acquisitions (Details)		12 Months Ended
	Feb. 21, 2018 USD ($)	Dec. 31, 2018 USD ($) property	Dec. 31, 2017 USD ($) property	Jan. 31, 2018 a restaurant
Acquisitions of Income Properties
Number of real estate properties | property		4
Amount allocated of total acquisition cost
Weighted average amortization period of intangible assets		14 years
Weighted average amortization period of intangible liabilities		14 years
LandShark Bar and Grill
Amount allocated of total acquisition cost
Number of restaurants | restaurant				2
Acres | a				6
Florida
Amount allocated of total acquisition cost
Tenant Contributions		$ 1,900,000
Net cash investment		26,500,000
Aspen, Colorado
Amount allocated of total acquisition cost
Tenant Contributions	$ 1,500,000	1,500,000
Net cash investment	$ 1,500,000
Real Estate Operations
Acquisitions of Income Properties
Payments to Acquire Commercial Real Estate		$ 106,636,566
Single-tenant
Acquisitions of Income Properties
Number of real estate properties | property		11
Single-tenant | Aspen, Colorado
Acquisitions of Income Properties
Payments to Acquire Commercial Real Estate		$ 28,000,000
Multi-tenant
Acquisitions of Income Properties
Number of real estate properties | property		4
2017 acquisitions of income property subject to a lease | Real Estate Operations
Acquisitions of Income Properties
Payments to Acquire Commercial Real Estate			$ 79,800,000
Aggregate acquisition cost including capitalized acquisition costs			$ 80,600,000
Amount allocated of total acquisition cost
Weighted average amortization period of intangible assets			8 years 10 months 24 days
Weighted average amortization period of intangible liabilities			8 years 10 months 24 days
2017 acquisitions of income property subject to a lease | Real Estate Operations | Nonrecurring basis
Acquisitions of Income Properties
Land			$ 28,000,000
Buildings and improvements			45,200,000
Intangible assets pertaining to the in-place lease value, leasing fees and above market lease value			9,300,000
Intangible liabilities for below market lease value			$ 1,900,000
2017 acquisitions of income property subject to a lease | Single-tenant
Acquisitions of Income Properties
Number of real estate properties | property			4
2017 acquisitions of income property subject to a lease | Multi-tenant
Acquisitions of Income Properties
Number of real estate properties | property			2
2018 acquisitions of income property subject to a lease | Real Estate Operations
Acquisitions of Income Properties
Aggregate acquisition cost including capitalized acquisition costs			$ 107,800,000
Amount allocated of total acquisition cost
Weighted average amortization period of intangible assets		13 years 2 months 12 days
Weighted average amortization period of intangible liabilities		13 years 2 months 12 days
2018 acquisitions of income property subject to a lease | Real Estate Operations | Nonrecurring basis
Acquisitions of Income Properties
Land			47,900,000
Buildings and improvements			45,600,000
Intangible assets pertaining to the in-place lease value, leasing fees and above market lease value			15,600,000
Intangible liabilities for below market lease value			$ 1,300,000
2018 acquisitions of income property subject to a lease | Single-tenant
Acquisitions of Income Properties
Number of real estate properties | property			11