OTHER BALANCE SHEET AMOUNTS - Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accrued compensation	$ 47,667	$ 33,626
Accrued commissions	13,329	18,834
Accrued interest	5,435	8,625
Other accrued expenses	24,234	16,990
Total accrued expenses	$ 90,665	$ 78,075