SEGMENT INFORMATION - Capital Expenditures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information
Capital expenditures	$ 105,956	$ 309,130
Operating Segments | Triple-Net Leased Properties
Segment Reporting Information
Capital expenditures	5,668	93,809
Operating Segments | Senior Living Operations
Segment Reporting Information
Capital expenditures	30,577	21,325
Operating Segments | Office Operations
Segment Reporting Information
Capital expenditures	$ 69,711	$ 193,996