REVENUES - Revenue recognized by timing of transfer of service (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 34,628	$ 8,323	$ 62,470	$ 15,993
Revenues recognized at a point in time
Disaggregation of Revenue [Line Items]
Revenues	24,432	100	42,169	100
Revenues from services delivered over time
Disaggregation of Revenue [Line Items]
Revenues	$ 10,196	$ 8,223	$ 20,301	$ 15,893