DISPOSITIONS - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) property parcel	Mar. 31, 2017 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations
Vacant parcels sold | parcel	1
Proceeds from sale of real estate | $	$ 170.2
Impairment of real estate | $	$ 7.0	$ 5.2
Medical Office Buildings
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations
Number of real estate properties sold	2
Senior Living Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations
Number of real estate properties sold	6
Triple-Net Leased Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations
Number of real estate properties sold	5