FAIR VALUES OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jul. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Assets:
Cash and cash equivalents	$ 588,343			$ 106,363
Escrow deposits and restricted cash	40,147			39,739
Non-mortgage loans receivable, net	56,844			63,724
Debt securities, available-for-sale, carrying value	231,168			237,360
Liabilities:
Long-term debt and short-term borrowings, gross	12,140,667			12,245,802
Redeemable OP Units, fair value	129,600			171,200
Brookdale Senior Living
Assets:
Cash and cash equivalents		$ 162,000
Non-mortgage loans receivable, net		45,000
Liabilities:
Warrants and Rights Outstanding		$ 28,000
Non-Mortgage Loan Receivable
Assets:
Non-mortgage loans receivable, net	56,844			63,724
Non-mortgage loans receivable, fair value	56,832			63,538
Secured/mortgage loans and other, net
Assets:
Debt securities, held-to-maturity	555,483			645,546
Debt securities, held-to-maturity, fair value	487,373			646,925
Secured/mortgage loans and other, net | Brookdale Senior Living
Assets:
Debt securities, held-to-maturity			$ 78,000
Government-Sponsored Pooled Loan Investments
Assets:
Debt securities, available-for-sale, carrying value	48,969			59,066
Carrying Value
Assets:
Cash and cash equivalents	588,343			106,363
Escrow deposits and restricted cash	40,147			39,739
Derivative instruments	195			738
Liabilities:
Derivative instruments	29,925			12,987
Redeemable OP Units, carrying amount	129,576			171,178
Carrying Value | Brookdale Senior Living
Liabilities:
Warrants and Rights Outstanding	26,940			0
Carrying Value | Non-Mortgage Loan Receivable
Assets:
Non-mortgage loans receivable, net	56,844			63,724
Carrying Value | Secured/mortgage loans and other, net
Assets:
Debt securities, held-to-maturity	555,483			645,546
Carrying Value | Marketable debt securities
Assets:
Debt securities, available-for-sale, carrying value	231,168			237,360
Carrying Value | Government-Sponsored Pooled Loan Investments
Assets:
Debt securities, available-for-sale, carrying value	48,969			59,066
Fair Value
Assets:
Cash and cash equivalents, fair value	588,343			106,363
Escrow deposits and restricted cash	40,147			39,739
Derivative instruments	195			738
Liabilities:
Long-term debt and short-term borrowings, fair value	12,882,340			12,778,758
Derivative instruments	29,925			12,987
Redeemable OP Units, fair value	129,576			171,178
Fair Value | Brookdale Senior Living
Liabilities:
Warrants and Rights Outstanding	26,940			0
Fair Value | Non-Mortgage Loan Receivable
Assets:
Non-mortgage loans receivable, fair value	56,832			63,538
Fair Value | Secured/mortgage loans and other, net
Assets:
Debt securities, held-to-maturity, fair value	487,373			646,925
Fair Value | Marketable debt securities
Assets:
Debt securities, available-for-sale, carrying value	231,168			237,360
Fair Value | Government-Sponsored Pooled Loan Investments
Assets:
Debt securities, available-for-sale, carrying value	$ 48,969			$ 59,066