ORGANIZATION AND SIGINIFICANT ACCOUNTING POLICIES - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 211,436,000	$ 220,143,000
Restricted cash	117,155,000	79,363,000
Total cash, cash equivalents and restricted cash	$ 328,591,000	$ 299,506,000	$ 201,450,000	$ 278,655,000