DISPOSITIONS - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016 USD ($) installment	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) property installment	Jun. 30, 2015 USD ($) property	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on real estate dispositions, net	$ (1)	$ 277	$ (1)	$ 277
Impairment of real estate			14,500	28,700
Impairment of long-lived assets to be disposed of			0	13,000
2016 Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from disposition of assets, including termination fees			63,800
Gain on real estate dispositions, net			$ 32,000
2016 Dispositions | Triple-Net Leased Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold | property			3
2016 Dispositions | Seniors Housing Communities | MOB operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold | property			1
2016 Dispositions | Medical Office Buildings | MOB operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold | property			1
2015 Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from disposition of assets, including termination fees				423,300
Gain on real estate dispositions, net				32,600
Lease termination fees				5,500
Deferred gain on sale of property		$ 18,100		$ 18,100
Deferred gain on sale of property, term					5 years
2015 Dispositions | Triple-Net Leased Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold | property				30
2015 Dispositions | Medical Office Buildings | MOB operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold | property				25
CCP
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount charge for Service Fee			$ 2,500
Durations of services provided			1 year
Income related to Service Fee	$ 600		$ 1,200
Number of quarterly installments | installment	4		4