BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 52,714	$ 26,579	$ 17,406
Restricted cash	2,535	19,538	4,672
Total cash, cash equivalents and restricted cash	$ 55,249	$ 46,117	$ 22,078	$ 19,256