INCOME PROPERTIES AND LEASES - General Information (Details)			9 Months Ended
	Jul. 16, 2019 USD ($) Options	May 23, 2019 USD ($) ft²	Sep. 30, 2019 USD ($) ft² Options property	Sep. 30, 2018 USD ($) ft² building property	Aug. 07, 2019 USD ($) a	Jun. 24, 2019 USD ($) ft²	Feb. 21, 2019 USD ($) ft²	Dec. 31, 2018 property	May 26, 2018 USD ($)
Acquisitions of Income Properties
Number of real estate properties | property								4
Payments to Acquire Commercial Real Estate			$ 90,029,000
Area of real estate property | ft²			219,333
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate			$ 32,419,693
Aggregate outstanding principal balance			32,500,000
Number of properties sold | property				4
Ground Lease Loan, 400 Josephine Street, Austin, TX
Acquisitions of Income Properties
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate			16,344,761
Aggregate outstanding principal balance			$ 16,250,000
Daytona Beach, FL
Acquisitions of Income Properties
Sales price									$ 11,400,000
2019 acquisitions of income property subject to lease
Acquisitions of Income Properties
Number of real estate properties | property			9
Payments to Acquire Commercial Real Estate			$ 90,000,000
Aggregate acquisition cost including capitalized acquisition costs			$ 90,600,000
Amount allocated of total acquisition cost
Weighted average amortization period of intangible assets			9 years 9 months 18 days
2019 acquisitions of income property subject to lease | Nonrecurring basis
Acquisitions of Income Properties
Land			$ 27,800,000
Buildings and improvements			37,700,000
Intangible assets pertaining to the in-place lease value, leasing fees and above market lease value			9,200,000
Intangible liabilities for below market lease value			400,000
2018 acquisitions of income property subject to a lease
Acquisitions of Income Properties
Number of real estate properties | property				1
Payments to Acquire Commercial Real Estate				$ 28,000,000
Aggregate acquisition cost including capitalized acquisition costs				$ 29,000,000
Amount allocated of total acquisition cost
Weighted average amortization period of intangible assets				20 years
Weighted average amortization period of intangible liabilities				20 years
2018 acquisitions of income property subject to a lease | Nonrecurring basis
Acquisitions of Income Properties
Land				$ 12,000,000
Buildings and improvements				15,000,000
Intangible assets pertaining to the in-place lease value, leasing fees and above market lease value				2,800,000
Intangible liabilities for below market lease value				$ 800,000
Concierge Office Building
Acquisitions of Income Properties
Area of real estate property | ft²				22,012
Williamson Business Park office building
Acquisitions of Income Properties
Area of real estate property | ft²				15,360
Gain on Sale				$ 3,700,000
Gain on sale of properties (in dollars per share)				$ 0.49
Area of real estate property leased | ft²				7,600
Lease term				5 years
Mason Commerce Center
Acquisitions of Income Properties
Area of real estate property | ft²				30,720
Number of office building | building				2
Whole Foods | Sarasota, FL | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Acquisitions of Income Properties
Sales price							$ 24,620,000
Area of real estate property | ft²							59,000
Gain on Sale			6,900,000
Gain on sale of properties (in dollars per share)			0.96
3600 Peterson | Santa Clara, CA | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Acquisitions of Income Properties
Sales price						$ 37,000,000
Area of real estate property | ft²						76,000
Gain on Sale			9,000,000
Gain on sale of properties (in dollars per share)			1.36
The Grove | Winter Park, FL | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Acquisitions of Income Properties
Sales price		$ 18,250,000
Gain on Sale			2,800,000
Gain on sale of properties (in dollars per share)			0.42
Area of real estate property leased | ft²		112,000
Wawa Sale | Winter Park, FL | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Acquisitions of Income Properties
Sales price					$ 2,800,000
Area of real estate property | a					1.56
Gain on Sale			2,100,000
Gain on sale of properties (in dollars per share)			0.33
Beachfront restaurant properties | Daytona Beach, FL | Cocina 214
Acquisitions of Income Properties
Amount funded to tenants	$ 1,000,000
Collection of lease rent	300,000
Payments for Tenant Improvements	$ 693,000
Beachfront restaurant properties | Daytona Beach, FL | Broken Hook LLC
Acquisitions of Income Properties
Lease term	10 years
Option to extend	true
Number of renewal options | Options	4
Renewal term	5 years
2019 acquisitions of income property subject to lease - Carpenter Hotel
Acquisitions of Income Properties
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate			$ 16,300,000
Number Of Tenant Repurchase Options | Options			2