SENIOR NOTES PAYABLE AND OTHER DEBT - Mortgages (Details) $ in Thousands, $ in Millions		1 Months Ended	12 Months Ended
	Sep. 21, 2021 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2022 USD ($) senior_housing loan property	Dec. 31, 2021 USD ($)	Sep. 30, 2021 CAD ($)
Debt Instrument [Line Items]
Weighted average maturity period of mortgage loans			4 years 6 months
Unamortized fair value adjustment			$ 23,535	$ 32,888
Minimum percentage of total unencumbered assets as a percentage of unsecured debt required to be maintained (as a percent)			150.00%
New Senior Investment Group Inc. Acquisition
Debt Instrument [Line Items]
Mortgage debt assumed in transaction	$ 482,500
Mortgage Loans and Other
Debt Instrument [Line Items]
Number of mortgage loans | loan			113
Principal amount of debt			$ 2,400,000
Number of properties securing debt | property			105
Number of mortgage loans with fixed interest rate | senior_housing			98
Mortgage loans with fixed interest rate			$ 2,000,000
Number of mortgage loans with variable interest rate | senior_housing			15
Mortgage loans with variable interest rate			$ 400,500
Repayments of debt			$ 600	$ 284,700
Mortgage Loans and Other | New Senior Investment Group Inc. Acquisition
Debt Instrument [Line Items]
Unamortized fair value adjustment					$ 25.4
Mortgage Loans and Other | New Senior Investment Group Inc. Acquisition
Debt Instrument [Line Items]
Mortgage debt assumed in transaction		$ 482,500
Mortgage Loans and Other | Fixed Rate Debt
Debt Instrument [Line Items]
Weighted interest rate			3.70%
Mortgage Loans and Other | Variable Rate Debt
Debt Instrument [Line Items]
Weighted interest rate			5.10%
Mortgage Loans and Other | Minimum
Debt Instrument [Line Items]
Long-term debt, percentage bearing fixed interest			0.00%
Long-term debt, percentage bearing variable interest			3.63%
Mortgage Loans and Other | Maximum
Debt Instrument [Line Items]
Long-term debt, percentage bearing fixed interest			13.01%
Long-term debt, percentage bearing variable interest			6.85%