FAIR VALUES OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets:
Cash and cash equivalents	$ 2,848,115	$ 106,363
Escrow deposits and restricted cash	38,144	39,739
Non-mortgage loans receivable, net	44,301	63,724
Debt securities, available-for-sale, carrying value	189,024	237,360
Liabilities:
Long-term debt and short-term borrowings, gross	14,256,769	12,245,802
Redeemable OP Units, fair value	100,800	171,200
Non-Mortgage Loan Receivable
Assets:
Non-mortgage loans receivable, net	44,301	63,724
Non-mortgage loans receivable, fair value	39,915	63,538
Secured/mortgage loans and other, net
Assets:
Debt securities, held-to-maturity	567,247	645,546
Debt securities, held-to-maturity, fair value	444,187	646,925
Government-Sponsored Pooled Loan Investments
Assets:
Debt securities, available-for-sale, carrying value	56,470	59,066
Carrying Value
Assets:
Cash and cash equivalents	2,848,115	106,363
Escrow deposits and restricted cash	38,144	39,739
Derivative instruments	1,676	738
Liabilities:
Derivative instruments	30,413	12,987
Redeemable OP Units, carrying amount	100,763	171,178
Carrying Value | Non-Mortgage Loan Receivable
Assets:
Non-mortgage loans receivable, net	44,301	63,724
Carrying Value | Secured/mortgage loans and other, net
Assets:
Debt securities, held-to-maturity	567,247	645,546
Carrying Value | Marketable debt securities
Assets:
Debt securities, available-for-sale, carrying value	189,024	237,360
Carrying Value | Government-Sponsored Pooled Loan Investments
Assets:
Debt securities, available-for-sale, carrying value	56,470	59,066
Fair Value
Assets:
Cash and cash equivalents, fair value	2,848,115	106,363
Escrow deposits and restricted cash	38,144	39,739
Derivative instruments	1,676	738
Liabilities:
Long-term debt and short-term borrowings, fair value	14,223,577	12,778,758
Derivative instruments	30,413	12,987
Redeemable OP Units, fair value	100,763	171,178
Fair Value | Non-Mortgage Loan Receivable
Assets:
Non-mortgage loans receivable, fair value	39,915	63,538
Fair Value | Secured/mortgage loans and other, net
Assets:
Debt securities, held-to-maturity, fair value	444,187	646,925
Fair Value | Marketable debt securities
Assets:
Debt securities, available-for-sale, carrying value	189,024	237,360
Fair Value | Government-Sponsored Pooled Loan Investments
Assets:
Debt securities, available-for-sale, carrying value	$ 56,470	$ 59,066