REVENUE - Other Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues	$ 25,472	$ 34,565	$ 77,686	$ 76,099
Other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues	$ (941)	$ 602	$ (976)	$ 1,709