EQUITY AND CASH COMPENSATION UNDER THE PPG AGREEMENTS - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
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 for cash portion of reimbursement of expenses	$ 738,000	$ 836,000	$ 2,200,000	$ 1,300,000
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	$ 20.00	$ 20.00