EQUITY AND CASH COMPENSATION UNDER THE PPG AGREEMENTS - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 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	$ 789,000	$ 821,000	$ 3,000,000.0	$ 2,100,000
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