QUARTERLY SUPPLEMENTAL FINANCIAL DATA (UNAUDITED) (Parenthetical) (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017		Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue	$ 70,143	$ 77,550	$ 56,149	$ 43,572	$ 115,867	[1],[2]	$ 61,683	$ 102,513	[1]	$ 55,566	$ 247,414	$ 335,629	$ 198,886
One-time charge due to enactment of the Tax Cuts and Jobs Act (TCJA)					11,500
License Fee [Member] | Samsung Display Co., Ltd [Member]
Revenue					$ 45,000			$ 45,000

[1] Prior to the adoption of ASC 606 on January 1, 2018, the Company recorded as revenue the receipt of the semi-annual license fee payment of $45.0 million from SDC in the second and fourth quarters.

[2] The enactment of the Tax Cuts and Jobs Act in December 2017 resulted in a one-time charge of $11.5 million in the fourth quarter.