COMMITTMENTS AND CONTINGENCIES - Fair Value Supply Agreement (Details) - Supply Commitments - Fair Value, Inputs, Level 3 - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Accrued expenses and other short-term liabilities | Supply Agreement Liability - Short-term
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning of Period		$ 166
Payments		(166)
Transfer from long-term to current portion		0
Balance, End of Period		0
Accrued expenses and other short-term liabilities | Supply Agreement Liability - Short-term | Selling, general and administrative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
(Gain)/loss from change in fair value		0
Accrued expenses and other short-term liabilities | Above Market Supply Agreement Liability - Short- Term
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning of Period	$ 2,641	0
Payments	(1,546)	0
Transfer from long-term to current portion		3,216
Transfer to accounts payable	(164)
Balance, End of Period	303	2,864
Accrued expenses and other short-term liabilities | Above Market Supply Agreement Liability - Short- Term | Selling, general and administrative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
(Gain)/loss from change in fair value	$ (628)	(352)
Other Long-term Liabilities | Above Market Supply Agreement Liability - Long-term
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning of Period		2,648
Payments		(415)
Transfer from long-term to current portion		(3,216)
Balance, End of Period		57
Other Long-term Liabilities | Above Market Supply Agreement Liability - Long-term | Selling, general and administrative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
(Gain)/loss from change in fair value		$ 1,040