INCOME PROPERTIES - Acquisitions of Income Properties (Details)					6 Months Ended
	Apr. 28, 2017 USD ($) ft² a tenant	Apr. 06, 2017 USD ($) ft² a	Mar. 01, 2017 USD ($) ft² a property building	Jan. 27, 2017 USD ($) ft² a	Jun. 30, 2017 USD ($) property	Jun. 30, 2016 USD ($) property
2017 acquisitions of income property subject to a lease
Acquisitions of Income Properties
Purchase price					$ 40,000,000
2017 acquisitions of income property subject to a lease | Sarasota, Florida
Acquisitions of Income Properties
Purchase price				$ 4,100,000
2017 acquisitions of income property subject to a lease | Fort Worth, Texas
Acquisitions of Income Properties
Purchase price			$ 15,000,000
2017 acquisitions of income property subject to a lease | Boston, Massachusetts
Acquisitions of Income Properties
Purchase price		$ 6,300,000
2017 acquisitions of income property subject to a lease | Tampa, Florida
Acquisitions of Income Properties
Purchase price	$ 14,700,000.0
2017 acquisitions of income property subject to a lease | Commercial
Acquisitions of Income Properties
Aggregate acquisition cost including capitalized acquisition costs					40,700,000
Land acquired					18,000,000
Buildings and improvements acquired					19,300,000
Intangible assets acquired					4,900,000
Intangible liabilities assumed					$ 1,500,000
Weighted average amortization period of intangible assets					9 years 9 months 18 days
Weighted average amortization period of intangible liabilities					9 years 9 months 18 days
2017 acquisitions of income property subject to a lease | Commercial | Sarasota, Florida
Acquisitions of Income Properties
Area of real estate property | ft²				18,120
Acres | a				1.2
Occupancy Percentage				100.00%
Remaining lease term as of the acquisition date				5 years
2017 acquisitions of income property subject to a lease | Commercial | Fort Worth, Texas
Acquisitions of Income Properties
Area of real estate property | ft²			136,000
Acres | a			10.3
Number of land parcels | property			3
Occupancy Percentage			96.00%
2017 acquisitions of income property subject to a lease | Commercial | Fort Worth, Texas | Weighted average
Acquisitions of Income Properties
Remaining lease term as of the acquisition date			4 years 1 month 6 days
2017 acquisitions of income property subject to a lease | Commercial | Boston, Massachusetts
Acquisitions of Income Properties
Area of real estate property | ft²		22,500
Acres | a		2.6
Occupancy Percentage		100.00%
Remaining lease term as of the acquisition date		11 years 9 months 18 days
2017 acquisitions of income property subject to a lease | Commercial | Tampa, Florida
Acquisitions of Income Properties
Acres | a	5.3
Remaining lease term as of the acquisition date	13 years 10 months 24 days
2017 acquisitions of income property subject to a lease | Single-tenant
Acquisitions of Income Properties
Number of real estate properties | property					3
2017 acquisitions of income property subject to a lease | Single-tenant | Fort Worth, Texas
Acquisitions of Income Properties
Number of real estate properties | building			4
2017 acquisitions of income property subject to a lease | Single-tenant | Tampa, Florida
Acquisitions of Income Properties
Area of real estate property | ft²	45,000
Occupancy Percentage	100.00%
2017 acquisitions of income property subject to a lease | Multi-tenant
Acquisitions of Income Properties
Number of real estate properties | property					2
2017 acquisitions of income property subject to a lease | Multi-tenant | Fort Worth, Texas
Acquisitions of Income Properties
Number of real estate properties | building			1
2017 acquisitions of income property subject to a lease | Multi-tenant | Tampa, Florida
Acquisitions of Income Properties
Area of real estate property | ft²	6,715
Occupancy Percentage	100.00%
Number of tenants | tenant	2
2016 Acquisitions | Multi-tenant
Acquisitions of Income Properties
Number of acquisitions | property						1
Purchase price						$ 2,500,000