ORGANIZATION AND SIGINIFICANT ACCOUNTING POLICIES - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 199,805,000	$ 193,770,000
Restricted cash	47,541,000	84,885,000
Total cash, cash equivalents and restricted cash	$ 247,346,000	$ 278,655,000	$ 202,216,000	$ 126,263,000