RESTRUCTURING - Rollforward of Restructuring Charges (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Restructuring Reserve [Roll Forward]
December 31, 2018	$ 1,155
Net expense	1,038
Payments and Other Adjustments	(1,050)
June 30, 2019	1,143
Severance
Restructuring Reserve [Roll Forward]
December 31, 2018	1,105
Net expense	712
Payments and Other Adjustments	(677)
June 30, 2019	1,140
Contract Termination Costs
Restructuring Reserve [Roll Forward]
December 31, 2018	0
Net expense	43
Payments and Other Adjustments	(43)
June 30, 2019	0
Equipment moving costs
Restructuring Reserve [Roll Forward]
December 31, 2018	8
Net expense	227
Payments and Other Adjustments	(234)
June 30, 2019	1
Other exit costs
Restructuring Reserve [Roll Forward]
December 31, 2018	42
Net expense	56
Payments and Other Adjustments	(96)
June 30, 2019	$ 2