INCOME TAXES - Summary of Tax Effects of Temporary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Non-current deferred tax assets:
Net operating loss carryforwards	$ 353,358	$ 338,403
U.S. federal and state tax credits	242	189
Other non-U.S. deferred tax assets	11,327	13,980
Share-based compensation	1,658	2,010
Accrued expenses	1,205	2,691
Unrealized losses	10,351	9,011
Other	0	526
Non-current deferred tax liabilities:
Intangible assets	(8,133)	(8,325)
Depreciation	(441)	(302)
Other non-U.S. deferred tax liability	(7)	(998)
Other	(736)	0
Deferred tax assets net of deferred tax liabilities	368,824	357,185
Valuation allowance	(372,227)	(355,559)
Non-current deferred tax (liabilities) assets, net	$ (3,403)
Non-current deferred tax (liabilities) assets, net		$ 1,626