DISPOSITIONS - Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 29, 2016 USD ($) property	Mar. 31, 2016 USD ($) property installment	Mar. 31, 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		$ 0	$ 0
Lease termination fees			5,500
Deferred gain on sale of property, term				5 years
Impairment of real estate		10,300	19,200
Impairment of long-lived assets to be disposed of		0	5,200
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		54,500
Gain on real estate dispositions, net		$ 26,200
2016 Dispositions | Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from disposition of assets, including termination fees	$ 8,000
Gain on real estate dispositions, net	$ 4,500
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		2
2016 Dispositions | Triple-Net Leased Properties | Subsequent Event
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 | 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			337,200
Gain on real estate dispositions, net			28,200
Deferred gain on sale of property			$ 21,400
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			21
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			22
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
Number of quarterly installments | installment		4