INCOME TAXES - Differences Between Income Tax Provision (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. federal income tax provision (benefit) at statutory rate	$ (2,842)	$ 216	$ 12,651
Foreign income and losses taxed at different rates (1)	5,529	2,113	4,524
State income taxes, net of federal benefits, and state tax credits	5,297	720	(4,980)
Change in valuation allowances	(10,074)	(7,727)	(36,057)
Effect of income tax rate changes on deferred items (2)	(3,443)	1,544	20,466
Tax effects of intercompany transactions	0	607	3,332
Adjustments related to uncertain tax positions	(12,418)	18	1,824
Non-deductible stock-based compensation expense	6,355	3,239	5,002
Tax shortfalls on stock-based compensation awards	2,042	(335)	4,290
Federal research and development credits	3,447	(8,331)	(7,862)
Forgiveness of intercompany liabilities	67	(1,340)	(2,494)
Ordinary stock loss	0	(11,815)	0
Net operating loss expiration	12,537	0	0
Non-deductible or non-taxable items	(5,736)	20,134	6,848
Provision (benefit) for income taxes	$ 761	$ (957)	$ 7,544