DISPOSITIONS - Real Estate Assets Classified As Held For Sale (Details) $ in Thousands	Sep. 30, 2017 USD ($) property	Dec. 31, 2016 USD ($) property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Properties Held for Sale | property	22	7
Assets held for sale	$ 68,926	$ 54,961
Liabilities related to assets held for sale	$ 9,837	$ 1,462
Triple-Net Leased Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Properties Held for Sale | property	15	0
Assets held for sale	$ 16,142	$ 0
Liabilities related to assets held for sale	$ 8,522	$ 0
Office Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Properties Held for Sale | property	7	7
Assets held for sale	$ 52,784	$ 53,151
Liabilities related to assets held for sale	$ 1,315	$ 1,462
Senior Living Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Properties Held for Sale | property	0	0
Assets held for sale	$ 0	$ 1,810
Liabilities related to assets held for sale	$ 0	$ 0
Vacant Land Parcel | Senior Living Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Properties Held for Sale | property		1