Leases - Components of lease expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
LEASES
Operating lease cost	$ 8,373	$ 14,109
Short-term lease cost	2,577	7,254
Variable lease cost	624	521
Sublease income	(295)	(72)
Total lease cost	$ 11,279	$ 21,812
Operating Leases, Rent Expense, Net			$ 21,600