RESTRUCTURING CHARGES - Restructuring charges (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 2,300	$ 1,206	$ 4,219	$ 10,310
Workforce reduction
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	2,263	1,149	4,131	10,218
Other restructuring costs
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 37	$ 57	$ 88	$ 92