SEGMENT INFORMATION - Capital Expenditures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information
Capital expenditures	$ 104,012	$ 129,589	$ 209,968	$ 438,719
Operating Segments | Triple-Net Leased Properties
Segment Reporting Information
Capital expenditures	15,340	48,143	21,008	141,952
Operating Segments | Senior Living Operations
Segment Reporting Information
Capital expenditures	24,177	30,056	54,754	51,381
Operating Segments | Office Operations
Segment Reporting Information
Capital expenditures	$ 64,495	$ 51,390	$ 134,206	$ 245,386