SEGMENT INFORMATION - Capital Expenditures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information
Capital expenditures	$ 129,205	$ 117,214	$ 339,173	$ 555,933
Operating Segments | Triple-Net Leased Properties
Segment Reporting Information
Capital expenditures	10,773	9,954	31,781	151,906
Operating Segments | Senior Living Operations
Segment Reporting Information
Capital expenditures	36,138	45,152	90,892	96,533
Operating Segments | Office Operations
Segment Reporting Information
Capital expenditures	$ 82,294	$ 62,108	$ 216,500	$ 307,494