SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Investment in Unconsolidated Joint Venture (Details) $ in Thousands	Jan. 02, 2018 USD ($) Property director	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Schedule of Equity Method Investments [Line Items]
Investment in joint venture		$ 348,950	$ 0
Enlivant Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of properties | Property	172
Enlivant Joint Venture
Schedule of Equity Method Investments [Line Items]
Cash contributed to acquire equity interests	$ 352,700
Equity interest in joint venture	49.00%
Outstanding indebtedness	$ 791,300
Net working capital	22,900
Aggregate portfolio value	$ 1,490,000
Number of directors appointed by Sabra | director	3
Number of directors on board | director	7
Investment in joint venture		$ 349,000