INVESTMENT IN REAL ESTATE PROPERTIES - Summarized Financial Information for Enlivant Joint Venture (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance Sheet Amounts
Total assets		$ 5,966,707	$ 5,985,603
Total liabilities		2,587,177	2,576,375
Member’s deficit		3,379,530	3,409,228	$ 3,488,460	$ 3,254,747
Income Statement Amounts
Total revenues		569,545	598,569	661,736
Other-than-temporary impairment		164,126	0	0
Loss from unconsolidated joint venture		(192,081)	(16,599)	(6,796)
Enlivant Joint Venture
Income Statement Amounts
Company’s share of net (loss) income		(17,184)	2,546	6,449
Basis adjustments		10,771	19,145	13,245
Other-than-temporary impairment	$ 164,100	164,126	0	0
Loss from unconsolidated joint venture		(192,081)	(16,599)	(6,796)
Enlivant Joint Venture
Balance Sheet Amounts
Total assets		467,762	490,541
Total liabilities		822,063	824,410
Member’s deficit		(354,301)	(333,869)
Income Statement Amounts
Total revenues		274,693	299,031	312,055
Operating expenses		265,194	240,331	231,659
Net (loss) income		(35,276)	$ 5,196	$ 13,161
Funding payments beyond contractual requirements		$ 20,000