SEGMENT INFORMATION - Capital Expenditures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Capital expenditures	$ 117,214	$ 1,440,229	$ 555,933	$ 1,591,286
Operating Segments | Triple-Net Leased Properties
Segment Reporting Information [Line Items]
Capital expenditures	9,954	12,992	151,906	69,642
Operating Segments | Senior Living Operations
Segment Reporting Information [Line Items]
Capital expenditures	45,152	26,495	96,533	70,297
Operating Segments | Office Operations
Segment Reporting Information [Line Items]
Capital expenditures	$ 62,108	$ 1,400,742	$ 307,494	$ 1,451,347