INCOME PROPERTIES - 2016 Acquisitions (Details) $ in Millions		12 Months Ended
	Sep. 16, 2016 USD ($) property	Dec. 31, 2018 USD ($) property	Dec. 31, 2016 USD ($) property
Acquisitions of Income Properties
Amount allocated to below market lease value		$ 1.3
Weighted average amortization period of intangible assets		14 years
Weighted average amortization period of intangible liabilities		14 years
Number of properties in the disposal group | property		4
Notes Reduction			$ 23.1
2016 dispositions of income property subject to a lease | Sold
Acquisitions of Income Properties
Number of properties in the disposal group | property	14		19
Sales price			$ 74.3
Single-tenant | 2016 dispositions of income property subject to a lease | Sold
Acquisitions of Income Properties
Number of properties in the disposal group | property	14
Sales price	$ 51.6
Notes Reduction	$ 23.1
2016 acquisitions
Acquisitions of Income Properties
Amount allocated to intangible assets			20.0
Amount allocated to below market lease value			$ 1.1
2016 acquisitions | Real Estate Operations
Acquisitions of Income Properties
Number of income properties acquired | property			10
Aggregate purchase of income properties			$ 86.7
Weighted average amortization period of intangible assets			14 years 3 months 18 days
Weighted average amortization period of intangible liabilities			14 years 3 months 18 days
2016 acquisitions | Land
Acquisitions of Income Properties
Amount allocated to land, buildings and improvements			$ 40.4
2016 acquisitions | Building and building improvements
Acquisitions of Income Properties
Amount allocated to land, buildings and improvements			$ 27.4
2016 acquisitions | Single-tenant
Acquisitions of Income Properties
Number of income properties acquired | property			7
2016 acquisitions | Multi-tenant
Acquisitions of Income Properties
Number of income properties acquired | property			3