LEASES - Components of Lease Expense and Payments (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
LEASES
Operating lease cost	$ 4,151	$ 7,667
Short-term lease cost	867	1,578
Variable lease cost	288	1,250
Total operating lease cost	5,306	10,495
Operating cash flows, which were included in the measurement of lease liabilities		3,800
Lease liabilities arising from right-of-use assets		3,300
Finance lease cost:
Amortization of right-of-use asset	586	1,179
Variable costs	262	558
Total finance lease cost	848	1,737
Finance leases cost included in property, plant and equipment	$ 26,000	$ 26,000
Property, plant and equipment	us-gaap:PropertyPlantAndEquipmentGross	us-gaap:PropertyPlantAndEquipmentGross
Accumulated depreciation related to finance leases	$ 8,300	$ 8,300