RESTRUCTURING CHARGES - Schedule of Accrued Restructuring and Severance Costs (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accrued restructuring and severance costs rollforward
Balance at beginning of period	$ 1,578,000
Net accruals	0	$ 9,017,000
Balance at end of period	820,000
Employee compensation costs
Accrued restructuring and severance costs rollforward
Balance at beginning of period	1,578,000
Net accruals	0
Non-cash adjustments	0
Cash paid	(758,000)
Balance at end of period	$ 820,000