FAIR VALUE DISCLOSURES - Face Values, Carrying Amounts and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial assets:
Loans receivable	$ 71,520	$ 96,492
Preferred equity investments	43,014	43,851
Senior Notes
Financial liabilities:
Financial liabilities	1,300,000	1,300,000
Secured Indebtedness
Financial liabilities:
Financial liabilities	116,954	117,464
Carrying Amount
Financial assets:
Loans receivable	65,789	69,460
Preferred equity investments	43,425	44,262
Carrying Amount | Senior Notes
Financial liabilities:
Financial liabilities	1,307,658	1,307,394
Carrying Amount | Secured Indebtedness
Financial liabilities:
Financial liabilities	115,188	115,679
Fair Value
Financial assets:
Loans receivable	66,146	65,797
Preferred equity investments	43,834	43,825
Fair Value | Senior Notes
Financial liabilities:
Financial liabilities	1,301,575	1,270,877
Fair Value | Secured Indebtedness
Financial liabilities:
Financial liabilities	$ 104,244	$ 101,820