ORGANIZATION AND SIGINIFICANT ACCOUNTING POLICIES - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 193,770,000	$ 108,282,000
Restricted cash	84,885,000	17,981,000
Total cash, cash equivalents and restricted cash	$ 278,655,000	$ 126,263,000	$ 246,712,000	$ 94,425,000