EQUITY AND CASH COMPENSATION UNDER THE PPG AGREEMENTS - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017
Long-term Purchase Commitment [Line Items]
Percent of services payable in cash or shares	50.00%		50.00%
Issuance of common stock in connection with materials and license agreements (in shares)	0	0	0			0
New OLED Materials Agreement and OLED Materials Agreement [Member] | Cash Distribution
Long-term Purchase Commitment [Line Items]
Charges to expense (credit) for cash portion of reimbursement of expenses	$ (161,000)	$ 143,000	$ 200,000			$ 247,000
New OLED Materials Agreement and OLED Materials Agreement [Member] | Weighted Average
Long-term Purchase Commitment [Line Items]
Minimum average closing price of common stock (in dollars per share)				$ 20.00	$ 20.00