Universal Display (OLED) 10-Q 6 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 04, 2021
Cover [Abstract]
Entity Registrant Name	UNIVERSAL DISPLAY CORPORATION
Entity Central Index Key	0001005284
Trading Symbol	OLED
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Document Type	10-Q
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		47,139,687
Entity Current Reporting Status	Yes
Entity File Number	1-12031
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	23-2372688
Entity Address, Address Line One	375 Phillips Boulevard
Entity Address, City or Town	Ewing
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	08618
City Area Code	609
Local Phone Number	671-0980
Title of 12(b) Security	Common Stock, $0.01 par value
Security Exchange Name	NASDAQ
Entity Interactive Data Current	Yes
Document Quarterly Report	true
Document Transition Report	false

CONSOLIDATED BALANCE SHEETS (UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
CURRENT ASSETS:
Cash and cash equivalents	$ 726,279	$ 630,012
Short-term investments	720	99,996
Accounts receivable	91,327	82,261
Inventory	101,422	91,591
Other current assets	39,587	20,746
Total current assets	959,335	924,606
PROPERTY AND EQUIPMENT, net of accumulated depreciation of $76,756 and $72,493	107,815	102,113
ACQUIRED TECHNOLOGY, net of accumulated amortization of $158,197 and $153,050	65,106	70,253
OTHER INTANGIBLE ASSETS, net of accumulated amortization of $6,496 and $6,155	10,641	10,685
GOODWILL	15,535	15,535
INVESTMENTS	8,500	5,000
DEFERRED INCOME TAXES	36,864	37,695
OTHER ASSETS	106,704	103,341
TOTAL ASSETS	1,310,500	1,269,228
CURRENT LIABILITIES:
Accounts payable	14,741	13,801
Accrued expenses	19,171	41,404
Deferred revenue	128,546	105,215
Other current liabilities	3,874	4,540
Total current liabilities	166,332	164,960
DEFERRED REVENUE	49,578	57,086
RETIREMENT PLAN BENEFIT LIABILITY	79,246	78,527
OTHER LIABILITIES	62,876	55,941
Total liabilities	358,032	356,514
COMMITMENTS AND CONTINGENCIES (Note 15)
SHAREHOLDERS' EQUITY:
Preferred Stock, par value $0.01 per share, 5,000,000 shares authorized, 200,000 shares of Series A Nonconvertible Preferred Stock issued and outstanding (liquidation value of $7.50 per share or $1,500)	2	2
Common Stock, par value $0.01 per share, 200,000,000 shares authorized, 49,050,776 and 49,013,476 shares issued, and 47,685,128 and 47,647,828 shares outstanding, at March 31, 2021 and December 31, 2020, respectively	491	490
Additional paid-in capital	632,138	635,595
Retained earnings	396,130	353,930
Accumulated other comprehensive loss	(35,009)	(36,019)
Treasury stock, at cost (1,365,648 shares at March 31, 2021 and December 31, 2020)	(41,284)	(41,284)
Total shareholders’ equity	952,468	912,714
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 1,310,500	$ 1,269,228

CONSOLIDATED BALANCE SHEETS (_2

CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 76,756,000	$ 72,493,000
Finite-Lived Intangible Assets, Accumulated Amortization	158,197,000	153,050,000
Other Finite-Lived Intangible Assets, Accumulated Amortization	$ 6,496,000	$ 6,155,000
SHAREHOLDERS' EQUITY:
Preferred Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred Stock, shares authorized ( in shares)	5,000,000	5,000,000
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized (in shares)	200,000,000	200,000,000
Common Stock, shares issued (in shares)	49,050,776	49,013,476
Common Stock, shares outstanding (in shares)	47,685,128	47,647,828
Treasury Stock
Treasury stock, shares	1,365,648	1,365,648
Series A Nonconvertible Preferred Stock [Member]
Shareholders' Equity A Nonconvertible Preferred Stock
Preferred Stock, shares issued (in shares)	200,000	200,000
Preferred Stock, shares outstanding (in shares)	200,000	200,000
Preferred Stock, liquidation value per share (in dollars per share)	$ 7.50	$ 7.50
Preferred Stock, liquidation value	$ 1,500,000	$ 1,500,000

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
REVENUE:
Total revenue	$ 134,000	$ 112,277
COST OF SALES	23,298	22,459
Gross margin	110,702	89,818
OPERATING EXPENSES:
Research and development	23,305	19,497
Selling, general and administrative	16,404	15,403
Amortization of acquired technology and other intangible assets	5,488	5,490
Patent costs	1,835	1,638
Royalty and license expense	112	3,284
Total operating expenses	47,144	45,312
OPERATING INCOME	63,558	44,506
Interest income, net	133	2,147
Other income, net	59	202
Interest and other income, net	192	2,349
INCOME BEFORE INCOME TAXES	63,750	46,855
INCOME TAX EXPENSE	(12,063)	(8,700)
NET INCOME	$ 51,687	$ 38,155
NET INCOME PER COMMON SHARE:
BASIC	$ 1.09	$ 0.80
DILUTED	$ 1.08	$ 0.80
WEIGHTED AVERAGE SHARES USED IN COMPUTING NET INCOME PER COMMON SHARE:
BASIC	47,267,921	47,093,033
DILUTED	47,329,704	47,122,829
CASH DIVIDENDS DECLARED PER COMMON SHARE	$ 0.20	$ 0.15
Material Sales
REVENUE:
Total revenue	$ 79,808	$ 66,575
Royalty And License Fees
REVENUE:
Total revenue	50,886	43,078
Contract Research Services
REVENUE:
Total revenue	$ 3,306	$ 2,624

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
NET INCOME	$ 51,687	$ 38,155
OTHER COMPREHENSIVE INCOME, NET OF TAX:
Unrealized (loss) gain on available-for-sale securities, net of tax of $17 and $525, respectively	(58)	1,855
Amortization of prior service cost and actuarial loss for retirement plan included in net periodic pension costs, net of tax of $335 and $182, respectively	1,174	638
Change in cumulative foreign currency translation adjustment	(106)	(33)
TOTAL OTHER COMPREHENSIVE INCOME	1,010	2,460
COMPREHENSIVE INCOME	$ 52,697	$ 40,615

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gain (loss) on available-for-sale securities, tax	$ 17	$ 525
Amortization of prior service cost and actuarial loss for retirement plan included in net periodic pension costs, tax	$ 335	$ 182

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Series A Nonconvertible Preferred Stock [Member]Preferred Stock [Member]
BALANCE at Dec. 31, 2019	$ 811,449	$ 489	$ 620,236	$ 249,003	$ (16,997)	$ (41,284)	$ 2
BALANCE (in shares) at Dec. 31, 2019		48,852,193				1,365,648	200,000
Net income	38,155			38,155
Other comprehensive income	2,460				2,460
Cash dividend	(7,098)			(7,098)
Issuance of common stock to employees	5,665		5,665
Issuance of common stock to employees (in shares)		80,483
Shares withheld for employee taxes	$ (4,816)		(4,816)
Shares withheld for employee taxes (in shares)		(30,437)
Common shares repurchased (in shares)	0
Issuance of common stock to Board of Directors and Scientific Advisory Board	$ 554		554
Issuance of common stock to Board of Directors and Scientific Advisory Board (in shares)		5,678
Issuance of common stock to employees under an ESPP	328		328
Issuance of common stock to employees under an ESPP (in shares)		2,315
BALANCE at Mar. 31, 2020	846,697	$ 489	621,967	280,060	(14,537)	$ (41,284)	$ 2
BALANCE (in shares) at Mar. 31, 2020		48,910,232				1,365,648	200,000
BALANCE at Dec. 31, 2020	912,714	$ 490	635,595	353,930	(36,019)	$ (41,284)	$ 2
BALANCE (in shares) at Dec. 31, 2020		49,013,476				1,365,648	200,000
Net income	51,687			51,687
Other comprehensive income	1,010				1,010
Cash dividend	(9,487)			(9,487)
Issuance of common stock to employees	5,116	$ 1	5,115
Issuance of common stock to employees (in shares)		53,123
Shares withheld for employee taxes	$ (9,634)		(9,634)
Shares withheld for employee taxes (in shares)		(22,048)
Common shares repurchased (in shares)	0
Issuance of common stock to Board of Directors and Scientific Advisory Board	$ 630		630
Issuance of common stock to Board of Directors and Scientific Advisory Board (in shares)		4,443
Issuance of common stock to employees under an ESPP	432		432
Issuance of common stock to employees under an ESPP (in shares)		1,782
BALANCE at Mar. 31, 2021	$ 952,468	$ 491	$ 632,138	$ 396,130	$ (35,009)	$ (41,284)	$ 2
BALANCE (in shares) at Mar. 31, 2021		49,050,776				1,365,648	200,000

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 51,687,000	$ 38,155,000
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred revenue and recognition of unbilled receivables	(57,648,000)	(40,511,000)
Depreciation	4,263,000	3,615,000
Amortization of intangibles	5,488,000	5,490,000
Change in excess inventory reserve	667,000	611,000
Amortization of premium and discount on investments, net	(70,000)	(2,005,000)
Stock-based compensation to employees	5,200,000	5,735,000
Stock-based compensation to Board of Directors and Scientific Advisory Board	330,000	254,000
Deferred income tax expense	515,000	940,000
Retirement plan expense	2,228,000	1,414,000
Decrease (increase) in assets:
Accounts receivable	(9,066,000)	(22,140,000)
Inventory	(10,498,000)	(10,726,000)
Other current assets	5,400,000	7,706,000
Other assets	(7,133,000)	(3,245,000)
Increase (decrease) in liabilities:
Accounts payable and accrued expenses	(21,136,000)	(29,340,000)
Other current liabilities	(666,000)	3,114,000
Deferred revenue	53,000,000	43,685,000
Other liabilities	6,935,000	2,994,000
Net cash provided by operating activities	29,496,000	5,746,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(9,938,000)	(4,782,000)
Purchases of intangibles	(298,000)
Purchases of investments	(4,220,000)	(148,592,000)
Proceeds from sale and maturity of investments	100,000,000	250,400,000
Net cash provided by investing activities	85,544,000	97,026,000
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	348,000	259,000
Payment of withholding taxes related to stock-based compensation to employees	(9,634,000)	(4,816,000)
Cash dividends paid	(9,487,000)	(7,098,000)
Net cash used in financing activities	(18,773,000)	(11,655,000)
INCREASE IN CASH AND CASH EQUIVALENTS	96,267,000	91,117,000
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	630,012,000	131,627,000
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 726,279,000	$ 222,744,000

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) Non-Cash Activities - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Other Significant Noncash Transactions [Line Items]
Unrealized (loss) gain on available-for-sale securities	$ (66)	$ 2,380
Net change in accounts payable and accrued expenses related to purchases of property and equipment	(27)	689
Common Stock Issued to Board of Directors and Scientific Advisory Board that was Earned and Accrued for in Previous Period [Member]
Other Significant Noncash Transactions [Line Items]
Other significant noncash transaction, value of consideration received	$ 300	$ 300

BUSINESS

BUSINESS	3 Months Ended
	Mar. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
BUSINESS	1. BUSINESS: Universal Display Corporation and its subsidiaries (the Company) is a leader in the research, development and commercialization of organic light emitting diode (OLED) technologies and materials for use in display and solid-state lighting applications. OLEDs are thin, lightweight and power-efficient solid-state devices that emit light that can be manufactured on both flexible and rigid substrates, making them highly suitable for use in full-color displays and as lighting products. OLED displays are capturing a growing share of the display market, especially in the mobile phone, television, wearable, tablet, notebook and personal computer, augmented reality (AR), virtual reality (VR) and automotive markets. The Company believes this is because OLEDs offer potential advantages over competing display technologies with respect to power efficiency, contrast ratio, viewing angle, video response time, form factor and manufacturing cost. The Company also believes that OLED lighting products have the potential to replace many existing light sources in the future because of their high-power efficiency, excellent color rendering index, low operating temperature and novel form factor. The Company’s technology leadership, intellectual property position, and the Company’s more than 20 years of experience working closely with leading OLED display manufacturers are some of the competitive advantages that should enable the Company to continue to share in the revenues from OLED displays and lighting products as they gain wider acceptance. The Company’s primary business strategy is to (1) develop new OLED materials and sell existing and any new materials to product manufacturers of products for display applications, such as mobile phones, televisions, wearables, tablets, portable media devices, notebook computers, personal computers and automotive applications, and specialty and general lighting products; and (2) further develop and license the Company’s proprietary OLED technologies to those manufacturers. The Company has established a significant portfolio of proprietary OLED technologies and materials, primarily through internal research and development efforts and acquisitions of patents and patent applications, as well as maintaining long-standing, and establishing new relationships with world-class universities, research institutions and strategic manufacturing partnerships. The Company currently owns, exclusively licenses or has the sole right to sublicense more than 5,000 patents issued and pending worldwide. The Company manufactures and sells its proprietary OLED materials to customers for evaluation and use in commercial OLED products. The Company also enters into agreements with manufacturers of OLED display and lighting products under which it grants them licenses to practice under the Company’s patents and to use the Company's proprietary know-how. At the same time, the Company works with these and other companies that are evaluating the Company's OLED technologies and materials for possible use in commercial OLED display and lighting products.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES: Interim Financial Information In the opinion of management, the accompanying unaudited Consolidated Financial Statements contain all adjustments (consisting of only normal recurring adjustments) necessary to present fairly the Company’s financial position as of March 31, 2021 and results of operations for the three months ended March 31, 2021 and 2020, and cash flows for the three months ended March 31, 2021 and 2020. While management believes that the disclosures presented are adequate to make the information not misleading, these unaudited Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and the notes thereto in the Company’s latest year-end Consolidated Financial Statements, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. The results of the Company’s operations for any interim period are not necessarily indicative of the results of operations for any other interim period or for the full year. Principles of Consolidation The Consolidated Financial Statements include the accounts of Universal Display Corporation and its wholly owned subsidiaries, UDC, Inc., UDC Ireland Limited (UDC Ireland), Universal Display Corporation Hong Kong, Limited, Universal Display Corporation Korea, Y.H., Universal Display Corporation Japan GK, Universal Display Corporation China, Ltd., Adesis, Inc. (Adesis), UDC Ventures LLC, OVJP Corporation (OVJP Corp) and OLED Material Manufacturing Limited (OMM). All intercompany transactions and accounts have been eliminated. In November 2020, a wholly-owned subsidiary of UDC Ireland, OMM , was formed as an Ireland limited company. Based out of Shannon, Ireland, OMM was formed to increase the Company’s production capacity to meet market demand and diversify the manufacturing base due to evolving industry requirements. Management’s Use of Estimates The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The estimates made are principally in the areas of revenue recognition including estimates of material unit sales and royalties, the useful life of acquired intangibles, lease liabilities, right-of-use assets, the use and recoverability of inventories, intangibles, investments and income taxes including realization of deferred tax assets, stock-based compensation and retirement benefit plan liabilities. Actual results could differ from those estimates. Inventories Inventories consist of raw materials, work-in-process and finished goods, including inventory consigned to customers, and are stated at the lower of cost, determined on a first-in, first-out basis, or net realizable value. Inventory valuation and firm committed purchase order assessments are performed on a quarterly basis and those items that are identified to be obsolete or in excess of forecasted usage are written down to their estimated realizable value. Estimates of realizable value are based upon management’s analyses and assumptions, including, but not limited to, forecasted sales levels by product, expected product lifecycle, product development plans and future demand requirements. A 12-month rolling forecast based on factors, including, but not limited to, production cycles, anticipated product orders, marketing forecasts, backlog, and shipment activities is used in the inventory analysis. If market conditions are less favorable than forecasts or actual demand from customers is lower than estimates, additional inventory write-downs may be required. If demand is higher than expected, inventories that had previously been written down may be sold. Fair Value of Financial Instruments The carrying values of accounts receivable, other current assets, accounts payable and other current liabilities approximate fair value in the accompanying Consolidated Financial Statements due to the short-term nature of those instruments. The Company’s other financial instruments, which include cash equivalents and investments, are carried at fair value. Minority Equity Investments The Company accounts for minority equity investments in companies that are not accounted for under the equity method as equity securities without readily determinable fair values. The fair value of these securities is based on original cost less impairments, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer. Under this method, the share of income or loss of such companies is not included in the Consolidated Statements of Income. The carrying value of these investments is included in investments on the Consolidated Balance Sheets. The Company’s policy is to recognize an impairment in the value of its minority equity investments when clear evidence of an impairment exists. Factors considered in the assessment include a significant adverse change in the regulatory, economic, or technological environment, the completion of new equity financing that may indicate a decrease in value, the failure to complete new equity financing arrangements after seeking to raise additional funds, or the commencement of proceedings under which the assets of the business may be placed in receivership or liquidated to satisfy the claims of debt and equity stakeholders. Leases The Company is a lessee in operating leases primarily incurred to facilitate the expansion of manufacturing, research and development, and selling, general and administrative activities. At contract inception, the Company determines if an arrangement is or contains a lease, and if so recognizes a right-of-use asset and lease liability at the lease commencement date. For operating leases, the lease liability is measured at the present value of the unpaid lease payments at the lease commencement date, whereas for finance leases, the lease liability is initially measured at the present value of the unpaid lease payments and subsequently measured at amortized cost using the interest method. Operating lease right-of-use assets are included in other assets on the Consolidated Balance Sheets. The short-term portion of operating lease liabilities is included in other current liabilities on the Consolidated Balance Sheets and the long-term portion is included in other liabilities on the Consolidated Balance Sheets. As of March 31, 2021, the Company had no leases that qualified as financing arrangements. Key estimates and judgments include how the Company determines the discount rate used to discount the unpaid lease payments to present value and the lease term. The Company monitors for events or changes in circumstances that could potentially require recognizing an impairment loss. Revenue Recognition and Deferred Revenue Material sales relate to the Company’s sale of its OLED materials for incorporation into its customers’ commercial OLED products or for their OLED development and evaluation activities. Revenue associated with material sales is generally recognized at the time title passes, which is typically at the time of shipment or at the time of delivery, depending upon the contractual agreement between the parties. Revenue may be recognized after control of the material passes in the event the transaction price includes variable consideration. For example, a customer may be provided an extended opportunity to stock materials prior to use in mass production and given a general right of return not conditioned on breaches of warranties associated with the specific product. In such circumstances, revenue will be recognized at the earlier of the expiration of the customer’s general right of return or once it becomes unlikely that the customer will exercise its right of return. The rights and benefits to the Company’s OLED technologies are conveyed to the customer through technology license agreements and material supply agreements. The Company believes that the licenses and materials sold under these combined agreements are not distinct from each other for financial reporting purposes and as such, are accounted for as a single performance obligation. Accordingly, total contract consideration, including material, license and royalty fees, is estimated and recognized over the contract term based on material units sold at the estimated per unit fee over the life of the contract. Various estimates are relied upon to recognize revenue. The Company estimates total material units to be purchased by its customers over the contract term based on historical trends, industry estimates and its forecast process. Management uses the expected value method to estimate the material per unit fee. Additionally, management estimates the total sales-based royalties based on the estimated net sales revenue of its customers over the contract term. Contract research services revenue is revenue earned by Adesis by providing chemical materials synthesis research, development and commercialization for non-OLED applications on a contractual basis. These services range from intermediates for structure-activity relationship studies, reference agents and building blocks for combinatorial synthesis, re-synthesis of key intermediates, specialty organic chemistry needs, and selective toll manufacturing. These services are provided to third-party pharmaceutical and life sciences firms and other technology firms at fixed costs or on an annual contract basis. Revenue is recognized as services are performed with billing schedules and payment terms negotiated on a contract-by-contract basis. Payments received in excess of revenue recognized are recorded as deferred revenue. In other cases, services may be provided and revenue is recognized before the customer is invoiced. In these cases, revenue recognized will exceed amounts billed and the difference, representing amounts which are currently unbillable to the customer pursuant to contractual terms, is recorded as an unbilled receivable. Technology development and support revenue is revenue earned from development and technology evaluation agreements and commercialization assistance fees, along with, to a minimal extent, government contracts. Relating to the Company’s government contracts, the Company may receive reimbursements by government entities for all or a portion of the research and development costs the Company incurs. Revenues are recognized as services are performed, proportionally as research and development costs are incurred, or as defined milestones are achieved. Technology development and support revenue is included in contract research services on the Consolidated Statements of Income. In 2018, the Company entered into a commercial patent license agreement with Samsung Display Co., Ltd. (SDC). This agreement, which covers the manufacture and sale of specified OLED display materials, was effective as of January 1, 2018 and lasts through the end of 2022 with an additional two-year extension option. Under this agreement, the Company is being paid a license fee, payable in quarterly installments over the agreement term of five years. The agreement conveys to SDC the non-exclusive right to use certain of the Company's intellectual property assets for a limited period of time that is less than the estimated life of the assets. At the same time the Company entered into the current commercial license agreement with SDC, the Company also entered into a new supplemental material purchase agreement with SDC. Under the supplemental material purchase agreement, SDC agrees to purchase from the Company a minimum amount of phosphorescent emitter materials for use in the manufacture of licensed products. This minimum commitment is subject to SDC’s requirements for phosphorescent emitter materials and the Company’s ability to meet these requirements over the term of the supplemental agreement. In 2015, the Company entered into an OLED patent license agreement and an OLED commercial supply agreement with LG Display Co., Ltd. (LG Display) which were effective as of January 1, 2015 and superseded the existing 2007 commercial supply agreement between the parties. The terms of the agreements were set to expire by the end of 2022. The patent license agreement provides LG Display a non-exclusive, royalty bearing portfolio license to make and sell OLED displays under the Company's patent portfolio. The patent license calls for license fees, prepaid royalties and running royalties on licensed products. The agreements include customary provisions relating to warranties, indemnities, confidentiality, assignability and business terms. The agreements provide for certain other minimum obligations relating to the volume of material sales anticipated over the life of the agreements as well as minimum royalty revenue to be generated under the patent license agreement. The Company generates revenue under these agreements that are predominantly tied to LG Display’s sales of OLED licensed products. The OLED commercial supply agreement provides for the sale of materials for use by LG Display, which may include phosphorescent emitters and host materials. In 2021, the Company entered into amendments of the OLED patent license agreement and the OLED commercial supply agreement with LG Display, which were effective as of January 1, 2021. The amended agreements included a term extension and are set to expire by the end of 2025. In 2016, the Company entered into long-term, multi-year OLED patent license and material purchase agreements with Tianma Micro-electronics Co., Ltd. (Tianma). Under the license agreement, the Company has granted Tianma non-exclusive license rights under various patents owned or controlled by the Company to manufacture and sell OLED display products. The license agreement calls for license fees and running royalties on licensed products. Additionally, the Company supplies phosphorescent OLED materials to Tianma for use in its licensed products. In 2017, the Company entered into long-term, multi-year agreements with BOE Technology Group Co., Ltd. (BOE). Under these agreements, the Company has granted BOE non-exclusive license rights under various patents owned or controlled by the Company to manufacture and sell OLED display products. The Company supplies phosphorescent OLED materials to BOE for use in its licensed products. In 2018, the Company entered into long-term, multi-year OLED patent license and material purchase agreements with Visionox Technology, Inc. (Visionox). Under the license agreement, the Company granted certain of Visionox’s affiliates a non-exclusive license rights under various patents owned or controlled by the Company to manufacture and sell OLED display products. The license agreement calls for license fees and running royalties on licensed products. Additionally, the Company supplies phosphorescent OLED materials to Visionox for use in its licensed products. On April 22, 2021, the Company announced that it had extended the Visionox agreement by entering into new five-year In 2019, the Company entered into an evaluation and commercial supply relationship with Wuhan China Star Optoelectronics Semiconductor Display Technology Co., Ltd. (CSOT). In 2020, the Company entered into long-term, multi-year agreements with CSOT. Under these agreements, the Company has granted CSOT non-exclusive license rights under various patents owned or controlled by the Company to manufacture and sell OLED display products. The Company also supplies phosphorescent OLED materials to CSOT for use in its licensed products. All material sales transactions that are not variable consideration transactions are billed and due within 90 days and substantially all are transacted in U.S. dollars. Cost of Sales Cost of sales consists of labor and material costs associated with the production of materials processed at the Company's manufacturing partners and at the Company's internal manufacturing processing facility. The Company’s portion of cost of sales also includes depreciation of manufacturing equipment, as well as manufacturing overhead costs and inventory adjustments for excess and obsolete inventory. Research and Development Expenditures for research and development are charged to expense as incurred. Patent Costs Costs associated with patent applications, patent prosecution, patent defense and the maintenance of patents are charged to expense as incurred. Costs to successfully defend a challenge to a patent are capitalized to the extent of an evident increase in the value of the patent. Costs that relate to an unsuccessful outcome are charged to expense. Amortization of Acquired Technology Amortization costs primarily relate to technology acquired from BASF and Fujifilm. These acquisitions were completed in the years ended December 31, 2016 and 2012, respectively. Acquisition costs are being amortized over a period of 10 years Amortization of Other Intangible Assets Other intangible assets relate to the Adesis acquisition and the Irish EPA license acquisition and are being amortized over a period of 10 to 15 years. See Note 7 for further discussion. Translation of Foreign Currency Financial Statements and Foreign Currency Transactions The Company’s reporting currency is the U.S. dollar. The functional currency for the UDC Ireland subsidiary is also the U.S. dollar and the functional currency for the OMM subsidiary and each of the Company's Asia-Pacific foreign subsidiaries is its local currency. The Company translates the amounts included in the Consolidated Statements of Income from OMM and its Asia-Pacific foreign subsidiaries into U.S. dollars at weighted-average exchange rates, which the Company believes are representative of the actual exchange rates on the dates of the transactions. The Company's foreign subsidiaries' assets and liabilities are translated into U.S. dollars from the local currency at the actual exchange rates as of the end of each reporting date, and the Company records the resulting foreign exchange translation adjustments in the Consolidated Balance Sheets as a component of accumulated other comprehensive loss. The overall effect of the translation of foreign currency and foreign currency transactions to date has been insignificant. Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained. Recognized income tax positions are measured at the largest amount of which the likelihood of realization is greater than 50%. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs. The Company records interest and penalties, if any, related to unrecognized tax benefits as a component of tax expense. Share-Based Payment Awards The Company recognizes in the Consolidated Statements of Income the grant-date fair value of equity-based awards such as shares issued under employee stock purchase plans, restricted stock awards, restricted stock units and performance unit awards issued to employees and directors. The grant-date fair value of stock awards is based on the closing price of the stock on the date of grant. The fair value of share-based awards is recognized as compensation expense on a straight-line basis over the requisite service period, net of forfeitures. The Company issues new shares upon the respective grant, exercise or vesting of the share-based payment awards, as applicable. Performance unit awards are subject to either a performance-based or market-based vesting requirement. For performance-based vesting, the grant-date fair value of the award, based on fair value of the Company's common stock, is recognized over the service period based on an assessment of the likelihood that the applicable performance goals will be achieved and compensation expense is periodically adjusted based on actual and expected performance. Compensation expense for performance unit awards with market-based vesting is calculated based on the estimated fair value as of the grant date utilizing a Monte Carlo simulation model and is recognized over the service period on a straight-line basis.

CASH, CASH EQUIVALENTS AND INVE

CASH, CASH EQUIVALENTS AND INVESTMENTS	3 Months Ended
	Mar. 31, 2021
Cash And Cash Equivalents [Abstract]
CASH, CASH EQUIVALENTS AND INVESTMENTS	3. CASH, CASH EQUIVALENTS AND INVESTMENTS: The Company’s portfolio of fixed income securities consists of term bank certificates of deposit, U.S. Government bonds and convertible notes. The Company considers all highly liquid debt instruments purchased with an original maturity (maturity at the purchase date) of three months or less to be cash equivalents. The Company classifies its remaining debt security investments as available-for-sale. These debt securities are carried at fair market value, with unrealized gains and losses reported in shareholders’ equity. Gains or losses on securities sold are based on the specific identification method. Cash and Cash Equivalents The following table provides details regarding the Company’s portfolio of cash and cash equivalents (in thousands): Amortized Unrealized Aggregate Cash and Cash Equivalents Classification Cost Gains (Losses) Market Value March 31, 2021 Cash accounts in banking institutions $ 160,850 $ — $ — $ 160,850 Money market accounts 16,438 — — 16,438 U.S. Government bonds 548,997 — (6 ) 548,991 $ 726,285 $ — $ (6 ) $ 726,279 December 31, 2020 Cash accounts in banking institutions $ 163,779 $ — $ — $ 163,779 Money market accounts 17,261 — — 17,261 U.S. Government bonds 448,970 6 (4 ) 448,972 $ 630,010 $ 6 $ (4 ) $ 630,012 Short-term Investments The following table provides details regarding the Company’s portfolio of short-term investments (in thousands): Amortized Unrealized Aggregate Short-term Investments Classification Cost Gains (Losses) Market Value March 31, 2021 Certificates of deposit $ 720 $ — $ — $ 720 $ 720 $ — $ — $ 720 December 31, 2020 U.S. Government bonds $ 99,929 $ 67 $ — $ 99,996 $ 99,929 $ 67 $ — $ 99,996 Minority Investments and Convertible Notes The Company’s portfolio of minority investments and convertible notes consist of investments in privately held early-stage companies primarily motivated to gain early access to new technology and are passive in nature in that the Company does not obtain representation on the board of directors of the companies in which it invests. Minority investments and convertible notes are included in investments on the Consolidated Balance Sheets. As of March 31, 2021, the Company had two minority investments with a total carrying value of $8.0 million accounted for as equity securities without readily determinable fair values. As of March 31, 2021, the Company had one convertible note investment with a fair value of $500,000 accounted for as an available-for-sale debt security with a level 3 fair value measurement.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	4. FAIR VALUE MEASUREMENTS: The following table provides the assets and liabilities carried at fair value measured on a recurring basis as of March 31, 2021 (in thousands): Fair Value Measurements, Using Total Carrying Value as of March 31, 2021 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents $ 548,991 $ 548,991 $ — $ — Short-term investments 720 720 — — Convertible notes 500 — — 500 The following table provides the assets and liabilities carried at fair value measured on a recurring basis as of December 31, 2020 (in thousands): Fair Value Measurements, Using Total Carrying Value as of December 31, 2020 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents $ 466,233 $ 466,233 $ — $ — Short-term investments 99,996 99,996 — — Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. Level 3 inputs are unobservable inputs based on management’s own assumptions used to measure assets and liabilities at fair value. A financial asset’s or liability’s classification is determined based on the lowest level input that is significant to the fair value measurement. Changes in fair value of the debt investments are recorded as unrealized gains and losses in accumulated other comprehensive loss on the Consolidated Balance Sheets and any credit losses on debt investments are recorded as an allowance for credit losses with an offset recognized in other income, net on the Consolidated Statements of Income. There were no credit losses on debt investments as of March 31, 2021 or December 31, 2020.

INVENTORY

INVENTORY	3 Months Ended
	Mar. 31, 2021
Inventory Disclosure [Abstract]
INVENTORY	5. INVENTORY: Inventory consisted of the following (in thousands): March 31, 2021 December 31, 2020 Raw materials $ 60,458 $ 46,843 Work-in-process 2,882 9,904 Finished goods 38,082 34,844 Inventory $ 101,422 $ 91,591 The Company recorded an increase in inventory reserve of $667,000 and $611,000 for the three months ended March 31, 2021 and 2020, respectively, due to excess inventory levels in certain products.

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	3 Months Ended
	Mar. 31, 2021
Property Plant And Equipment [Abstract]
PROPERTY AND EQUIPMENT	6. PROPERTY AND EQUIPMENT: Property and equipment, net consist of the following (in thousands): March 31, 2021 December 31, 2020 Land $ 2,642 $ 2,642 Building and improvements 55,321 53,568 Office and lab equipment 91,857 85,881 Furniture, fixtures and computer related assets 11,948 8,921 Construction-in-progress 22,803 23,594 184,571 174,606 Less: Accumulated depreciation (76,756 ) (72,493 ) Property and equipment, net $ 107,815 $ 102,113 Depreciation expense was $4.3 million and $3.6 million for the three months ended March 31, 2021 and 2020, respectively.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2021
Finite Lived Intangible Assets Net [Abstract]
GOODWILL AND INTANGIBLE ASSETS	7 . GOODWILL AND INTANGIBLE ASSETS: The Company monitors the recoverability of goodwill annually or whenever events or changes in circumstances indicate the carrying value may not be recoverable. Purchased intangible assets subject to amortization consist primarily of acquired technology and other intangible assets that include trade names, customer relationships, developed intellectual property (IP) processes and EPA licenses. Acquired Technology Acquired technology consists of acquired license rights for patents and know-how obtained from PD-LD, Inc., Motorola, BASF SE (BASF) and Fujifilm. These intangible assets consist of the following (in thousands): March 31, 2021 December 31, 2020 PD-LD, Inc. $ 1,481 $ 1,481 Motorola 15,909 15,909 BASF 95,989 95,989 Fujifilm 109,462 109,462 Other 462 462 223,303 223,303 Less: Accumulated amortization (158,197 ) (153,050 ) Acquired technology, net $ 65,106 $ 70,253 Amortization expense related to acquired technology was $5.1 million for both three-month periods ended March 31, 2021 and 2020. Amortization expense is included in amortization of acquired technology and other intangible assets expense line item on the Consolidated Statements of Income and is expected to be $15.5 million for the nine months ending December 31, 2021, $15.8 million in the year ending December 31, 2022, $9.7 million in the year ending December 31, 2023, $9.6 million in the years ending December 31, 2024 and 2025 and $4.9 million in total thereafter. Fujifilm Patent Acquisition On July 23, 2012, the Company entered into a Patent Sale Agreement with Fujifilm. Under the agreement, Fujifilm sold more than 1,200 OLED-related patents and patent applications in exchange for a cash payment of $105.0 million, plus costs incurred in connection with the purchase. The agreement contains customary representations and warranties and covenants, including respective covenants not to sue by both parties thereto. The agreement permitted the Company to assign all of its rights and obligations under the agreement to its affiliates, and the Company assigned, prior to the consummation of the transactions contemplated by the agreement, its rights and obligations to UDC Ireland, a wholly-owned subsidiary of the Company formed under the laws of the Republic of Ireland. The transactions contemplated by the agreement were consummated on July 26, 2012. The Company recorded the $105.0 million plus $4.5 million of purchase costs as acquired technology, which is being amortized over a period of 10 years. BASF Patent Acquisition On June 28, 2016, UDC Ireland entered into and consummated an IP Transfer Agreement with BASF. Under the IP Transfer Agreement, BASF sold to UDC Ireland all of its rights, title and interest to certain of its owned and co-owned intellectual property rights relating to the composition of, development, manufacture and use of OLED materials, including OLED lighting and display stack technology, as well as certain tangible assets. The intellectual property includes knowhow and more than 500 issued and pending patents in the area of phosphorescent materials and technologies. These assets were acquired in exchange for a cash payment of €86.8 million ($95.8 million). In addition, UDC Ireland also took on certain rights and obligations under three joint research and development agreements to which BASF was a party. The IP Transfer Agreement also contains customary representations, warranties and covenants of the parties. UDC Ireland recorded the payment of €86.8 million ($95.8 million) and acquisition costs incurred of $217,000 as acquired technology, which is being amortized over a period of 10 years. Other Intangible Assets As a result of the Adesis acquisition in June 2016, the Company recorded $16.8 million of other intangible assets, including $10.5 million assigned to customer relationships with a weighted average life of 11.5 years, $4.8 million of internally developed IP, processes and recipes with a weighted average life of 15 years, and $1.5 million assigned to trade name and trademarks with a weighted average life of 10 years. At March 31, 2021, these other intangible assets consist of the following (in thousands): March 31, 2021 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Customer relationships $ 10,520 $ (4,284 ) $ 6,236 Developed IP, processes and recipes 4,820 (1,507 ) 3,313 Trade name/Trademarks 1,500 (705 ) 795 Other 297 — 297 Total identifiable other intangible assets $ 17,137 $ (6,496 ) $ 10,641 Amortization expense related to other intangible assets was $341,000 and $345,000 for the three months ended March 31, 2021 and 2020, respectively. Amortization expense is included in amortization of acquired technology and other intangible assets expense line item on the Consolidated Statements of Income and is expected to be $1.1 million for the nine months ending December 31, 2021, $1.4 million for each of the next four fiscal years (2022 – 2025) and $3.9 million in total thereafter.

LEASES

LEASES	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
LEASES	8. LEASES: The Company has entered into operating leases to facilitate the expansion of its manufacturing, research and development, and selling, general and administrative activities. For purposes of calculating operating lease liabilities, lease terms may be deemed to include options to extend or terminate the lease when those events are reasonably certain to occur. The interest rate implicit in lease contracts is typically not readily determinable and as such the Company uses the appropriate incremental borrowing rate based on information available at the lease commencement date in determining the present value of the lease payments. Current lease agreements do not contain any residual value guarantees or material restrictive covenants. As of March 31, 2021, the Company did not have any finance leases and no additional operating leases that have not yet commenced. The following table presents the Company’s operating lease cost and supplemental cash flow information related to the Company’s operating leases (in thousands): Three Months Ended March 31, 2021 2020 Operating lease cost $ 615 $ 537 Non-cash activity: Right-of-use assets obtained in exchange for lease obligations $ 4,720 $ — The following table presents the Company’s operating right-of-use assets and liabilities (in thousands): March 31, 2021 December 31, 2020 Right-of-use assets $ 12,819 $ 8,750 Short-term lease liabilities 2,324 1,871 Long-term lease liabilities 10,495 6,879 The following table presents weighted average assumptions used to compute the Company’s right-of-use assets and lease liabilities: March 31, 2021 Weighted average remaining lease term (in years) 7.3 Weighted average discount rate 3.4 % As of March 31, 2021, current operating leases had remaining terms between two and eight years with options to extend the lease terms. Undiscounted future minimum lease payments as of March 31, 2021, by year and in the aggregate, having non-cancelable lease terms in excess of one year were as follows (in thousands): Maturities of Operating Lease Liabilities 2021 (1) $ 1,987 2022 2,541 2023 1,652 2024 1,474 2025 1,263 Thereafter 5,520 Total lease payments 14,437 Less: Imputed interest (1,618 ) Present value of lease payments $ 12,819 (1) Scheduled maturities of lease liabilities represent the time-period of April 1, 2021 to December 31, 2021.

RESEARCH AND LICENSE AGREEMENTS

RESEARCH AND LICENSE AGREEMENTS WITH PRINCETON UNIVERSITY, UNIVERSITY OF SOUTHERN CALIFORNIA AND THE UNIVERSITY OF MICHIGAN	3 Months Ended
	Mar. 31, 2021
Research And Development [Abstract]
RESEARCH AND LICENSE AGREEMENTS WITH PRINCETON UNIVERSITY, UNIVERSITY OF SOUTHERN CALIFORNIA AND THE UNIVERSITY OF MICHIGAN	9 . RESEARCH AND LICENSE AGREEMENTS WITH PRINCETON UNIVERSITY, UNIVERSITY OF SOUTHERN CALIFORNIA AND THE UNIVERSITY OF MICHIGAN: The Company has long-standing relationships with Princeton University (Princeton) and the University of Southern California (USC), dating back to 1994, for the conduct of research relating to the Company’s OLED and other organic thin-film technologies and materials. This research had been performed at Princeton under the direction of Professor Stephen R. Forrest and at USC under the direction of Professor Mark E. Thompson. Under an Amended License Agreement entered into in 1997 by the Company, Princeton and USC (as amended, the 1997 Amended License Agreement), Princeton and USC granted the Company worldwide, exclusive license rights, with rights to sublicense, to make, have made, use, lease and/or sell products and to practice processes based on patent applications and issued patents arising out of research performed by Princeton and USC for the Company. Under the 1997 Amended License Agreement, the Company pays Princeton royalties of 3% of the net sales price for licensed products it sells or 3% of the revenues the Company receives from its sublicensees for their sale of licensed products. The Company recorded royalty expense in connection with this agreement of $112,000 and $3.3 million for the three months ended March 31, 2021 and 2020. The decline in the royalty expense was primarily due to the expiration of patents relating to the licensed products, as specified in the Amended License Agreement. In 2006, Professor Forrest transferred from Princeton to the University of Michigan (Michigan) and the Company amended the 1997 Amended License Agreement to include Michigan as a party to that agreement. Also in connection with the transfer, the Company entered into a sponsored research agreement with USC under which the Company continues to fund organic electronics research being conducted by Professors Forrest and Thompson (the 2006 Research Agreement). Work by Professor Forrest is being funded through a subcontract between USC and Michigan. The 2006 Research Agreement extends through April 2023 The Company make s payments under the 2006 Research Agreement to USC on a quarterly basis as actual expenses are incurred. As of March 31 , 202 1 , the Company was obligated to pay USC up to $ million for work to be performed during the remaining extended term. The Company recorded research and development expense in connection with work performed under the 2006 Research Agreement of $ and $ for the three months ended March 3 1 , 202 1 and 20 20 , respectively .

EQUITY AND CASH COMPENSATION UN

EQUITY AND CASH COMPENSATION UNDER THE PPG AGREEMENTS	3 Months Ended
	Mar. 31, 2021
Long Term Commitment Excluding Unconditional Purchase Obligation [Abstract]
EQUITY AND CASH COMPENSATION UNDER THE PPG AGREEMENTS	10 . EQUITY AND CASH COMPENSATION UNDER THE PPG AGREEMENTS: On September 22, 2011, the Company entered into an Amended and Restated OLED Materials Supply and Service Agreement with PPG Industries, Inc. (PPG) (the New OLED Materials Agreement), which replaced the original OLED Materials Agreement with PPG effective as of October 1, 2011. The term of the New OLED Materials Agreement ran through December 31, 2015 and shall be automatically renewed for additional one-year terms, unless terminated by the Company by providing prior notice of one year or terminated by PPG by providing prior notice of two years. The agreement was automatically renewed through December 31, 2021. The New OLED Materials Agreement contains provisions that are substantially similar to those of the original OLED Materials Agreement. Under the New OLED Materials Agreement, PPG continues to assist the Company in developing its proprietary OLED materials and supplying the Company with those materials for evaluation purposes and for resale to its customers. Under the New OLED Materials Agreement, the Company compensates PPG on a cost-plus basis for the services provided during each calendar quarter. The Company is required to pay for some of these services in all cash. Up to 50% of the remaining services are payable, at the Company’s sole discretion, in cash or shares of the Company’s common stock, with the balance payable in cash. The actual number of shares of common stock issuable to PPG is determined based on the average closing price for the Company’s common stock during a specified number of days prior to the end of each calendar half-year period ending on March 31 and September 30. If, however, this average closing price is less than $20.00, the Company is required to compensate PPG in cash. No shares were issued for services to PPG for the three months ended March 31, 2021 or 2020. The Company is also required to reimburse PPG for raw materials used for research and development. The Company records the purchases of these raw materials as a current asset until such materials are used for research and development efforts. On February 23, 2021, the Company entered into an amendment to the New OLED Materials Agreement specifying operation and maintenance services that will be provided by PPG affiliate, PPG SCM Ireland Limited, to OMM, at the new manufacturing site in Shannon, Ireland, currently being leased by OMM for the production of OLED materials. Facility improvements and regulatory approvals are expected to be completed in the next 12 months and operations are scheduled to commence in early 2022. As with the initial New OLED Materials Agreement, the Company will compensate PPG on a cost-plus basis for the services provided at the Shannon manufacturing facility. The Company recorded research and development expense of $1.5 million and $473,000 for the three months ended March 31, 2021 and 2020, respectively, in relation to the cash portion of the reimbursement of expenses and work performed by PPG, excluding amounts paid for commercial chemicals.

SHAREHOLDERS' EQUITY

SHAREHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
SHAREHOLDERS' EQUITY	1 1 . SHAREHOLDERS’ EQUITY: Preferred Stock The Company’s Amended and Restated Articles of Incorporation authorize it to issue up to 5,000,000 shares of $0.01 par value preferred stock with designations, rights and preferences determined from time-to-time by the Company’s Board of Directors. Accordingly, the Company’s Board of Directors is empowered, without shareholder approval, to issue preferred stock with dividend, liquidation, conversion, voting or other rights superior to those of shareholders of the Company’s common stock. In 1995, the Company issued 200,000 shares of Series A Nonconvertible Preferred Stock (Series A) to American Biomimetics Corporation (ABC) pursuant to a certain Technology Transfer Agreement between the Company and ABC. The Series A shares have a liquidation value of $7.50 per share. Series A shareholders, as a single class, have the right to elect two members of the Company’s Board of Directors. This right has never been exercised. Holders of the Series A shares are entitled to one vote per share on matters which shareholders are generally entitled to vote. The Series A shareholders are not entitled to any dividends. As of March 31, 2021, the Company had issued 200,000 shares of preferred stock, all of which were outstanding. Common Stock The Company’s Amended and Restated Articles of Incorporation authorize it to issue up to 200,000,000 shares of $0.01 par value common stock. Each share of the Company’s common stock entitles the holder to one vote on all matters to be voted upon by the shareholders. As of March 31, 2021, the Company had issued 49,050,776 shares of common stock, of which 47,685,128 were outstanding. During the three months ended March 31, 2021 and 2020, the Company repurchased no shares of common stock. Scientific Advisory Board Awards During the three months ended March 31, 2021 and 2020, the Company granted a total of 1,400 and 1,926 shares, respectively, of fully vested common stock to non-employee members of the Scientific Advisory Board for services performed in 2020 and 2019, respectively. The fair value of shares issued to members of the Scientific Advisory Board was $300,000 for both three-month periods. Dividends During the three months ended March 31, 2021, the Company declared and paid cash dividends of $0.20 per common share, or $9.5 million, on the Company’s outstanding common stock. On May 4, 2021, the Company’s Board of Directors declared a second quarter dividend of $0.20 per common share to be paid on June 30, 2021 to all shareholders of record as of the close of business on June 15, 2021. All future dividends will be subject to the approval of the Company’s Board of Directors.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE LOSS	3 Months Ended
	Mar. 31, 2021
Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]
ACCUMULATED OTHER COMPREHENSIVE LOSS	1 2 . ACCUMULATED OTHER COMPREHENSIVE LOSS: Amounts related to the changes in accumulated other comprehensive loss were as follows (in thousands): Unrealized Gain (Loss) on Available-for-Sale Securities Net Unrealized Gain (Loss) on Retirement Plan (2) Change in Cumulative Foreign Currency Translation Adjustment Total Affected Line Items in the Consolidated Statements of Income Balance December 31, 2020, net of tax $ 91 $ (36,075 ) $ (35 ) $ (36,019 ) Other comprehensive loss before reclassification (58 ) — (106 ) (164 ) Reclassification to net income (1) — 1,174 — 1,174 Selling, general and administrative, research and development and cost of sales Change during period (58 ) 1,174 (106 ) 1,010 Balance March 31, 2021, net of tax $ 33 $ (34,901 ) $ (141 ) $ (35,009 ) Unrealized Gain (Loss) on Available-for-Sale Securities Net Unrealized Gain (Loss) on Retirement Plan (2) Change in Cumulative Foreign Currency Translation Adjustment Total Affected Line Items in the Consolidated Statements of Income Balance December 31, 2019, net of tax $ 191 $ (17,167 ) $ (21 ) $ (16,997 ) Other comprehensive gain before reclassification 1,855 — (33 ) 1,822 Reclassification to net income (1) — 638 — 638 Selling, general and administrative, research and development and cost of sales Change during period 1,855 638 (33 ) 2,460 Balance March 31, 2020, net of tax $ 2,046 $ (16,529 ) $ (54 ) $ (14,537 ) (1) The Company reclassified amortization of prior service cost and actuarial loss for its retirement plan from accumulated other comprehensive loss to net income of $1.2 million and $638,000 for the three months ended March 31, 2021 and 2020. (2) Refer to Note 14: Supplemental Executive Retirement Plan.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
STOCK-BASED COMPENSATION	1 3 . STOCK-BASED COMPENSATION: Equity Compensation Plan The Equity Compensation Plan provides for the granting of incentive and nonqualified stock options, shares of common stock, stock appreciation rights and performance units to employees, directors and consultants of the Company. Stock options are exercisable over periods determined by the Compensation Committee, but for no longer than 10 years from the grant date. Through March 31, 2021, the Company’s shareholders have approved increases in the number of shares reserved for issuance under the Equity Compensation Plan to 10,500,000, and have extended the term of the plan through 2024. As of March 31, 2021, there were 1,828,661 shares that remained available to be granted under the Equity Compensation Plan. Restricted Stock Awards and Units The Company has issued restricted stock awards and units to employees and non-employees with vesting terms of one to six years. The fair value is equal to the market price of the Company’s common stock on the date of grant for awards granted to employees and equal to the market price at the end of the reporting period for unvested non-employee awards or upon the date of vesting for vested non-employee awards. Expense for restricted stock awards and units is amortized ratably over the vesting period for the awards issued to employees and using a graded vesting method for the awards issued to non-employees. During the three months ended March 31, 2021, the Company granted 100,079 shares of restricted stock awards and restricted stock units to employees and non-employees, which had a total fair value of $22.7 million on the respective dates of grant, and will vest over three to five years from the date of grant, provided that the grantee is still an employee of the Company or is still providing services to the Company on the applicable vesting date. For the three months ended March 31, 2021 and 2020, the Company recorded, as compensation charges related to all restricted stock awards and units granted to employees and non-employees, selling, general and administrative expense of $3.6 million and $3.3 million, respectively, research and development expense of $1.2 million and $877,000, respectively, and cost of sales of $557,000 and $400,000, respectively. In connection with the vesting of restricted stock awards and units during the three months ended March 31, 2021 and 2020, 48,824 and 24,474 shares, respectively, with aggregate fair values of $9.4 million and $3.9 million, respectively, were withheld in satisfaction of tax withholding obligations and are reflected as a financing activity within the Consolidated Statements of Cash Flows. For the three months ended March 31, 2021 and 2020, the Company recorded as compensation charges related to all restricted stock units granted to non-employee members of the Scientific Advisory Board, whose unvested shares are marked to market each reporting period, research and development expense of $36,000 and credit of $43,000, respectively. The Company has granted restricted stock units to non-employee members of the Board of Directors with quarterly vesting over a period of approximately one year. The fair value is equal to the market price of the Company's common stock on the date of grant. The restricted stock units are issued and expense is recognized ratably over the vesting period. For the three months ended March 31, 2021 and 2020, the Company recorded compensation charges for services performed, related to all restricted stock units granted to non-employee members of the Board of Directors, selling, general and administrative expense of $294,000 and $297,000, respectively. In connection with the vesting of the restricted stock, the Company issued to non-employee members of the Board of Directors 1,353 and 1,614 shares, respectively, during the three months ended March 31, 2021 and 2020. Performance Unit Awards Each performance unit award is subject to both a performance-vesting requirement (either performance-based or market-based) and a service-vesting requirement. The performance-based vesting requirement is tied to the Company's cumulative revenue growth compared to the cumulative revenue growth of companies comprising the Nasdaq Electronics Components Index, as measured over a specific performance period. The market-based vesting requirement is tied to the Company's total shareholder return relative to the total shareholder return of companies comprising the Nasdaq Electronics Components Index, as measured over a specific performance period. The maximum number of performance units that may vest based on performance is two times the shares granted. Further, if the Company's total shareholder return is negative, the performance units may not vest at all. During the three months ended March 31, 2021, the Company granted 69,586 performance units, of which 34,791 units are subject to performance-based vesting requirements and 34,795 units are subject to market-based vesting requirements, and which will vest over the terms described below. The weighted average grant date fair value of the performance unit awards granted was $15.8 million for the three months ended March 31, 2021, as determined by the Company’s common stock on date of grant for the units with performance-based vesting and a Monte-Carlo simulation for the units with market-based vesting. For the three months ended March 31, 2021 and 2020, the Company recorded a selling, general and administrative credit of $211,000 and $811,000, respectively, research and development credit of $56,000 and $202,000, respectively, and cost of sales credit of $35,000 and $113,000, respectively, related to performance units. In connection with the vesting of performance units during the three months ended March 31, 2021 and 2020, 1,224 and 5,963 shares, respectively, with an aggregate fair value of $231,000 and $930,000, respectively, were withheld in satisfaction of tax withholding obligations and are reflected as a financing activity within the Consolidated Statements of Cash Flows. Employee Stock Purchase Plan On April 7, 2009, the Board of Directors of the Company adopted an Employee Stock Purchase Plan (ESPP). The ESPP was approved by the Company’s shareholders and became effective on June 25, 2009. The Company has reserved 1,000,000 shares of common stock for issuance under the ESPP. Unless terminated by the Board of Directors, the ESPP will expire when all reserved shares have been issued. Eligible employees may elect to contribute to the ESPP through payroll deductions during consecutive three-month purchase periods, the first of which began on July 1, 2009. Each employee who elects to participate will be deemed to have been granted an option to purchase shares of the Company’s common stock on the first day of the purchase period. Unless the employee opts out during the purchase period, the option will automatically be exercised on the last day of the period, which is the purchase date, based on the employee’s accumulated contributions to the ESPP. The purchase price will equal 85% of the lesser of the closing price per share of common stock on the first day of the period or the last business day of the period. Employees may allocate up to 10% of their base compensation to purchase shares of common stock under the ESPP; however, each employee may purchase no more than 12,500 shares on a given purchase date, and no employee may purchase more than $25,000 of common stock under the ESPP during a given calendar year. During the three months ended March 31, 2021 and 2020, the Company issued 1,782 and 2,315 shares, respectively, of its common stock under the ESPP, resulting in proceeds of $348,000 and $259,000, respectively. For the three months ended March 31, 2021 and 2020, the Company recorded charges of $23,000 and $22,000, respectively, to selling, general and administrative expense, $36,000 and $28,000, respectively, to research and development expense, and $25,000 and $19,000, respectively, to cost of sales related to the ESPP equal to the amount of the discount and the value of the look-back feature.

SUPPLEMENTAL EXECUTIVE RETIREME

SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN	3 Months Ended
	Mar. 31, 2021
Compensation And Retirement Disclosure [Abstract]
SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN	1 4 . SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN: On March 18, 2010, the Compensation Committee and the Board of Directors of the Company approved and adopted the Universal Display Corporation Supplemental Executive Retirement Plan (SERP). The SERP is currently unfunded and includes salary and bonus as part of the plan. The purpose of the SERP is to provide certain of the Company’s key employees with supplemental pension benefits following a cessation of their employment and to encourage their continued employment with the Company. As of March 31, 2021, there were seven participants in the SERP. The Company records amounts relating to the SERP based on calculations that incorporate various actuarial and other assumptions, including discount rates, rate of compensation increases, retirement dates and life expectancies. The net periodic costs are recognized as employees render the services necessary to earn the SERP benefits. The components of net periodic pension cost were as follows (in thousands): Three Months Ended March 31, 2021 2020 Service cost $ 428 $ 273 Interest cost 291 321 Amortization of prior service cost 275 275 Amortization of loss 1,234 545 Total net periodic benefit cost $ 2,228 $ 1,414

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	1 5 . COMMITMENTS AND CONTINGENCIES: Commitments Under the 2006 Research Agreement with USC, the Company is obligated to make certain payments to USC based on work performed by USC under that agreement, and by Michigan under its subcontractor agreement with USC. See Note 9 for further explanation. Under the terms of the 1997 Amended License Agreement, the Company is required to make minimum royalty payments to Princeton. See Note 9 for further explanation. The Company has agreements with six executive officers and 12 senior level employees which provide for certain cash and other benefits upon termination of employment of the officer or employee in connection with a change in control of the Company. If a covered person’s employment is terminated in connection with the change in control, the person is entitled to a lump-sum cash payment equal to two times (in the case of the executive officers) or either one or two times (in the case of the senior level employees) the sum of the average annual base salary and bonus of the person and immediate vesting of all stock options and other equity awards that may be outstanding at the date of the change in control, among other items. In order to manage manufacturing lead times and help ensure adequate material supply, the Company entered into the New OLED Materials Agreement (see Note 10) that allows PPG to procure and produce inventory based upon criteria as defined by the Company. These purchase commitments consist of firm, noncancelable and unconditional commitments. In certain instances, this agreement allows the Company the option to reschedule and adjust the Company’s requirements based on its business needs prior to firm orders being placed. As of March 31, 2021 and December 31, 2020, the Company had purchase commitments for inventory of $18.9 million and $13.7 million, respectively. Patent Related Challenges and Oppositions Each major jurisdiction in the world that issues patents provides both third parties and applicants an opportunity to seek a further review of an issued patent. The process for requesting and considering such reviews is specific to the jurisdiction that issued the patent in question, and generally does not provide for claims of monetary damages or a review of specific claims of infringement. The conclusions made by the reviewing administrative bodies tend to be appealable and generally are limited in scope and applicability to the specific claims and jurisdiction in question. The Company believes that opposition proceedings are frequently commenced in the ordinary course of business by third parties who may believe that one or more claims in a patent do not comply with the technical or legal requirements of the specific jurisdiction in which the patent was issued. The Company views these proceedings as reflective of its goal of obtaining the broadest legally permissible patent coverage permitted in each jurisdiction. Once a proceeding is initiated, as a general matter, the issued patent continues to be presumed valid until the jurisdiction’s applicable administrative body issues a final non-appealable decision. Depending on the jurisdiction, the outcome of these proceedings could include affirmation, denial or modification of some or all of the originally issued claims. The Company believes that as OLED technology becomes more established and its patent portfolio increases in size, so will the number of these proceedings. Below is a summary of an active proceeding that has been commenced against an issued patent that is exclusively licensed to the Company. The Company does not believe that the confirmation, loss or modification of the Company’s rights in any individual claim or set of claims that are the subject of the following legal proceeding would have a material impact on the Company’s material sales or licensing business or on the Company’s Consolidated Financial Statements, including its Consolidated Statements of Income, as a whole. However, as noted within the description, the following proceeding involves an issued patent that relates to the Company’s fundamental phosphorescent OLED technologies and the Company intends to vigorously defend against claims that, in the Company’s opinion, seek to restrict or reduce the scope of the originally issued claim, which may require the expenditure of significant amounts of the Company’s resources. In certain circumstances, when permitted, the Company may also utilize a proceeding to request modification of the claims to better distinguish the patented invention from any newly identified prior art and/or improve the claim scope of the patent relative to commercially important categories of the invention. Opposition to European Patent No. 1390962 On November 16, 2011, Osram AG and BASF SE each filed a Notice of Opposition to European Patent No. 1390962 (the EP '962 patent), which relates to the Company’s white phosphorescent OLED technology. The EP '962 patent, which was issued on February 16, 2011, is a European counterpart patent to U.S. patents 7,009,338 and 7,285,907. They are exclusively licensed to the Company by Princeton, and the Company is required to pay all legal costs and fees associated with this proceeding. The European Patent Office (EPO) combined the oppositions into a single opposition proceeding, and a hearing on this matter was held in December 2015, wherein the EPO Opposition Division revoked the patent claims for alleged insufficiencies under European Patent Convention Article 83. The Company believes the EPO's decision is erroneous and appealed the decision. Subsequent to the filing of the appeal, BASF withdrew its opposition to the patent. On appeal, the Appeals Division withdrew the lower Opposition Division’s rejections with respect to a portion of the original subject matter and remanded the matter to the lower Opposition Division for further consideration. The patent, as originally granted, is deemed valid during the pendency of the opposition process. At this time, based on its current knowledge, the Company believes that the patent being challenged should be declared valid and that a significant portion of the Company's claims should be upheld. However, the Company cannot make any assurances of this result. In addition to the above proceeding and now concluded proceedings which have been referenced in prior filings, from time to time, the Company may have other proceedings that are pending which relate to patents the Company acquired as part of the Fujifilm or BASF OLED patent acquisitions or which relate to technologies that are not currently widely used in the marketplace.

CONCENTRATION OF RISK

CONCENTRATION OF RISK	3 Months Ended
	Mar. 31, 2021
Risks And Uncertainties [Abstract]
CONCENTRATION OF RISK	1 6 . CONCENTRATION OF RISK: Revenues and accounts receivable from the Company's largest customers were as follows (in thousands): % of Total Revenue for the Three Months Ended March 31, Accounts Receivable as of Customer 2021 2020 March 31, 2021 A 36% 41% $ 6,204 B 23% 25% $ 20,769 C 20% 23% $ 22,802 D 12% 7% $ 17,740 Revenues from outside of North America represented approximately 97% and 98% of consolidated revenue for the three months ended March 31, 2021 and 2020, respectively. Revenues by geographic area are as follows (in thousands): Three Months Ended March 31, Country 2021 2020 South Korea $ 67,975 $ 69,425 China 60,504 37,834 Japan 1,315 1,787 Other non-U.S. locations 825 497 Total non-U.S. locations 130,619 109,543 United States 3,381 2,734 Total revenue $ 134,000 $ 112,277 The Company attributes revenue to different geographic areas on the basis of the location of the customer. Long-lived assets (net), by geographic area are as follows (in thousands): March 31, 2021 December 31, 2020 United States $ 99,678 $ 93,230 Other 8,137 8,883 Total long-lived assets $ 107,815 $ 102,113 Substantially all chemical materials were purchased from one supplier. See Note 10.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
INCOME TAXES	1 7 . The Company is subject to income taxes in both the United States and foreign jurisdictions. The effective income tax rate was an expense of 18.9% and 18.6% for the three months ended March 31, 2021 and 2020, respectively. The Company recorded an income tax expense of $12.1 million and $8.7 million for the three months ended March 31, 2021 and 2020, respectively. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent on the Company's ability to generate future taxable income to obtain benefit from the reversal of temporary differences, net operating loss carryforwards and tax credits. As part of its assessment , management considers the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax planning strategies. At this time there is no evidence to release the valuation allowance that has historically been recorded for the New Jersey research and development credit. On December 27, 2018 the Korean Supreme Court, citing prior cases, held that the applicable law and interpretation of the Korea-U.S. Tax Treaty were clear that only royalties paid with respect to Korean registered patents are Korean source income and subject to Korean withholding tax. Based on this decision, the Company has decided to litigate the Korean withholding taxes paid or withheld on the 2018, 2019 and 2020 royalty payments and has engaged a leading Korean law firm which has advised that there is a more-likely-than-not chance of success. As a result, as of March 31, 2021 and December 31, 2020, the Company has recorded a long-term asset of $43.4 million and $40.1 million, respectively, representing the allocation of withholding to non-Korean patents and a long-term liability of $35.9 million and $32.7 million, respectively, for estimated amounts due to the U.S. Federal government based on the amendment of U.S. tax returns for lower withholding amounts. With respect to the Korean withholding for the years 2011 through 2017, the Company has decided to continue the U.S.-Korean Mutual Agreement Procedure which was accepted by the Korean National Tax Service (KNTS) on September 15, 2017. The Company believes that it is more-likely-than-not that a favorable settlement will be reached resulting in a reduction of the Korean withholding taxes previously withheld since 2011. A long-term asset of $36.9 million for estimated refunds due from the Korean government, a long-term payable of $16.2 million for estimated amounts due to the U.S. Federal government based on amendment of prior year U.S. tax returns for the lower withholding amounts, and a reduction of deferred tax assets for foreign tax credits and research and development credits of $20.7 million has been recorded on the March 31, 2021 and December 31, 2020 Consolidated Balance Sheets for this matter. On October 30, 2018, the KNTS concluded a tax audit with LG Display that included the licensing and royalty payments made to UDC Ireland during the years 2015 through 2017. The KNTS questioned whether UDC Ireland was the beneficial owner of these payments and assessed UDC Ireland a charge of $13.2 million for withholding and interest for the three-year The Company’s federal income tax returns for the years 2017 to 2020 are open and subject to examination. The State of New Jersey is currently auditing the 2014 to 2017 tax returns of UDC, Inc. The state and foreign tax returns are open for a period of generally three to four years. The above estimates may change in the future and upon settlement.

REVENUE RECOGNITION

REVENUE RECOGNITION	3 Months Ended
	Mar. 31, 2021
Revenue From Contract With Customer [Abstract]
REVENUE RECOGNITION	1 8 . REVENUE RECOGNITION: Effective on January 1, 2018, the Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers (Topic 606) For both three-month periods ended March 31, 2021 and 2020, the Company recorded 98% 2% Contract Balances The following table provides information about assets and liabilities associated with our contracts from customers (in thousands): As of March 31, 2021 Accounts receivable $ 91,327 Short-term unbilled receivables 24,900 Long-term unbilled receivables — Short-term deferred revenue 128,546 Long-term deferred revenue 49,578 Short-term and long-term unbilled receivables are classified as other current assets and other assets, respectively, on the Consolidated Balance Sheets. The deferred revenue balance at March 31, 2021 will be recognized as materials are shipped to customers over the remaining contract periods. As of March 31, 2021, the Company had $19.4 million of backlog associated with committed purchase orders from its customers for phosphorescent emitter material. These orders are anticipated to be fulfilled within the next 90 days. Significant changes in the unbilled receivables and deferred liabilities balances for the three months ended March 31, 2021 and 2020, are as follows (in thousands): Three Months Ended March 31, 2021 Unbilled Receivables Deferred Revenue Balance at December 31, 2020 $ 10,429 $ (162,301 ) Revenue recognized that was previously included in deferred revenue — 33,439 Increases due to cash received — (53,000 ) Cumulative catch-up adjustment arising from changes in estimates of transaction price — 3,738 Unbilled receivables recognized 20,471 — Transferred to receivables from unbilled receivables (6,000 ) — Net change 14,471 (15,823 ) Balance at March 31, 2021 $ 24,900 $ (178,124 ) Three Months Ended March 31, 2020 Unbilled Receivables Deferred Revenue Balance at December 31, 2019 $ 1,362 $ (144,862 ) Revenue recognized that was previously included in deferred revenue — 38,749 Increases due to cash received — (43,685 ) Cumulative catch-up adjustment arising from changes in estimates of transaction price — 367 Unbilled receivables recognized 1,395 — Net change 1,395 (4,569 ) Balance at March 31, 2020 $ 2,757 $ (149,431 )

NET INCOME PER COMMON SHARE

NET INCOME PER COMMON SHARE	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
NET INCOME PER COMMON SHARE	1 9 . NET INCOME PER COMMON SHARE: The Company computes earnings per share in accordance with ASC Topic 260, Earnings per Share Basic net income per common share is computed by dividing net income allocated to common shareholders by the weighted-average number of shares of common stock outstanding for the period excluding unvested restricted stock units and performance units. Net income allocated to the holders of the Company's unvested restricted stock awards is calculated based on the shareholders proportionate share of weighted average shares of common stock outstanding on an if-converted basis. For purposes of determining diluted net income per common share, basic net income per share is further adjusted to include the effect of potential dilutive common shares outstanding, including stock options, restricted stock units and performance units, and the impact of shares to be issued under the E mployee Stock Purchase Plan . The following table is a reconciliation of net income and the shares used in calculating basic and diluted net income per common share for the three months ended March 31, 2021 and 2020 (in thousands, except share and per share data): Three Months Ended March 31, 2021 2020 Numerator: Net income $ 51,687 $ 38,155 Adjustment for Basic EPS: Earnings allocated to unvested shareholders (358 ) (339 ) Adjusted net income $ 51,329 $ 37,816 Denominator: Weighted average common shares outstanding – Basic 47,267,921 47,093,033 Effect of dilutive shares: Common stock equivalents arising from stock options and ESPP 165 441 Restricted stock awards and units and performance units 61,618 29,355 Weighted average common shares outstanding – Diluted 47,329,704 47,122,829 Net income per common share: Basic $ 1.09 $ 0.80 Diluted $ 1.08 $ 0.80 For the three months ended March 31, 2021 and 2020, the combined effects of unvested restricted stock awards, restricted stock units, performance unit awards and stock options of none and 14,112, respectively, were excluded from the calculation of diluted EPS as their impact would have been antidilutive.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Accounting	Interim Financial Information In the opinion of management, the accompanying unaudited Consolidated Financial Statements contain all adjustments (consisting of only normal recurring adjustments) necessary to present fairly the Company’s financial position as of March 31, 2021 and results of operations for the three months ended March 31, 2021 and 2020, and cash flows for the three months ended March 31, 2021 and 2020. While management believes that the disclosures presented are adequate to make the information not misleading, these unaudited Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and the notes thereto in the Company’s latest year-end Consolidated Financial Statements, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. The results of the Company’s operations for any interim period are not necessarily indicative of the results of operations for any other interim period or for the full year.
Principles of Consolidation	Principles of Consolidation The Consolidated Financial Statements include the accounts of Universal Display Corporation and its wholly owned subsidiaries, UDC, Inc., UDC Ireland Limited (UDC Ireland), Universal Display Corporation Hong Kong, Limited, Universal Display Corporation Korea, Y.H., Universal Display Corporation Japan GK, Universal Display Corporation China, Ltd., Adesis, Inc. (Adesis), UDC Ventures LLC, OVJP Corporation (OVJP Corp) and OLED Material Manufacturing Limited (OMM). All intercompany transactions and accounts have been eliminated. In November 2020, a wholly-owned subsidiary of UDC Ireland, OMM , was formed as an Ireland limited company. Based out of Shannon, Ireland, OMM was formed to increase the Company’s production capacity to meet market demand and diversify the manufacturing base due to evolving industry requirements.
Management's Use of Estimates	Management’s Use of Estimates The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The estimates made are principally in the areas of revenue recognition including estimates of material unit sales and royalties, the useful life of acquired intangibles, lease liabilities, right-of-use assets, the use and recoverability of inventories, intangibles, investments and income taxes including realization of deferred tax assets, stock-based compensation and retirement benefit plan liabilities. Actual results could differ from those estimates.
Inventories	Inventories Inventories consist of raw materials, work-in-process and finished goods, including inventory consigned to customers, and are stated at the lower of cost, determined on a first-in, first-out basis, or net realizable value. Inventory valuation and firm committed purchase order assessments are performed on a quarterly basis and those items that are identified to be obsolete or in excess of forecasted usage are written down to their estimated realizable value. Estimates of realizable value are based upon management’s analyses and assumptions, including, but not limited to, forecasted sales levels by product, expected product lifecycle, product development plans and future demand requirements. A 12-month rolling forecast based on factors, including, but not limited to, production cycles, anticipated product orders, marketing forecasts, backlog, and shipment activities is used in the inventory analysis. If market conditions are less favorable than forecasts or actual demand from customers is lower than estimates, additional inventory write-downs may be required. If demand is higher than expected, inventories that had previously been written down may be sold.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying values of accounts receivable, other current assets, accounts payable and other current liabilities approximate fair value in the accompanying Consolidated Financial Statements due to the short-term nature of those instruments. The Company’s other financial instruments, which include cash equivalents and investments, are carried at fair value.
Minority Equity Investments	Minority Equity Investments The Company accounts for minority equity investments in companies that are not accounted for under the equity method as equity securities without readily determinable fair values. The fair value of these securities is based on original cost less impairments, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer. Under this method, the share of income or loss of such companies is not included in the Consolidated Statements of Income. The carrying value of these investments is included in investments on the Consolidated Balance Sheets. The Company’s policy is to recognize an impairment in the value of its minority equity investments when clear evidence of an impairment exists. Factors considered in the assessment include a significant adverse change in the regulatory, economic, or technological environment, the completion of new equity financing that may indicate a decrease in value, the failure to complete new equity financing arrangements after seeking to raise additional funds, or the commencement of proceedings under which the assets of the business may be placed in receivership or liquidated to satisfy the claims of debt and equity stakeholders.
Leases	Leases The Company is a lessee in operating leases primarily incurred to facilitate the expansion of manufacturing, research and development, and selling, general and administrative activities. At contract inception, the Company determines if an arrangement is or contains a lease, and if so recognizes a right-of-use asset and lease liability at the lease commencement date. For operating leases, the lease liability is measured at the present value of the unpaid lease payments at the lease commencement date, whereas for finance leases, the lease liability is initially measured at the present value of the unpaid lease payments and subsequently measured at amortized cost using the interest method. Operating lease right-of-use assets are included in other assets on the Consolidated Balance Sheets. The short-term portion of operating lease liabilities is included in other current liabilities on the Consolidated Balance Sheets and the long-term portion is included in other liabilities on the Consolidated Balance Sheets. As of March 31, 2021, the Company had no leases that qualified as financing arrangements. Key estimates and judgments include how the Company determines the discount rate used to discount the unpaid lease payments to present value and the lease term. The Company monitors for events or changes in circumstances that could potentially require recognizing an impairment loss.
Revenue Recognition and Deferred Revenue	Revenue Recognition and Deferred Revenue Material sales relate to the Company’s sale of its OLED materials for incorporation into its customers’ commercial OLED products or for their OLED development and evaluation activities. Revenue associated with material sales is generally recognized at the time title passes, which is typically at the time of shipment or at the time of delivery, depending upon the contractual agreement between the parties. Revenue may be recognized after control of the material passes in the event the transaction price includes variable consideration. For example, a customer may be provided an extended opportunity to stock materials prior to use in mass production and given a general right of return not conditioned on breaches of warranties associated with the specific product. In such circumstances, revenue will be recognized at the earlier of the expiration of the customer’s general right of return or once it becomes unlikely that the customer will exercise its right of return. The rights and benefits to the Company’s OLED technologies are conveyed to the customer through technology license agreements and material supply agreements. The Company believes that the licenses and materials sold under these combined agreements are not distinct from each other for financial reporting purposes and as such, are accounted for as a single performance obligation. Accordingly, total contract consideration, including material, license and royalty fees, is estimated and recognized over the contract term based on material units sold at the estimated per unit fee over the life of the contract. Various estimates are relied upon to recognize revenue. The Company estimates total material units to be purchased by its customers over the contract term based on historical trends, industry estimates and its forecast process. Management uses the expected value method to estimate the material per unit fee. Additionally, management estimates the total sales-based royalties based on the estimated net sales revenue of its customers over the contract term. Contract research services revenue is revenue earned by Adesis by providing chemical materials synthesis research, development and commercialization for non-OLED applications on a contractual basis. These services range from intermediates for structure-activity relationship studies, reference agents and building blocks for combinatorial synthesis, re-synthesis of key intermediates, specialty organic chemistry needs, and selective toll manufacturing. These services are provided to third-party pharmaceutical and life sciences firms and other technology firms at fixed costs or on an annual contract basis. Revenue is recognized as services are performed with billing schedules and payment terms negotiated on a contract-by-contract basis. Payments received in excess of revenue recognized are recorded as deferred revenue. In other cases, services may be provided and revenue is recognized before the customer is invoiced. In these cases, revenue recognized will exceed amounts billed and the difference, representing amounts which are currently unbillable to the customer pursuant to contractual terms, is recorded as an unbilled receivable. Technology development and support revenue is revenue earned from development and technology evaluation agreements and commercialization assistance fees, along with, to a minimal extent, government contracts. Relating to the Company’s government contracts, the Company may receive reimbursements by government entities for all or a portion of the research and development costs the Company incurs. Revenues are recognized as services are performed, proportionally as research and development costs are incurred, or as defined milestones are achieved. Technology development and support revenue is included in contract research services on the Consolidated Statements of Income. In 2018, the Company entered into a commercial patent license agreement with Samsung Display Co., Ltd. (SDC). This agreement, which covers the manufacture and sale of specified OLED display materials, was effective as of January 1, 2018 and lasts through the end of 2022 with an additional two-year extension option. Under this agreement, the Company is being paid a license fee, payable in quarterly installments over the agreement term of five years. The agreement conveys to SDC the non-exclusive right to use certain of the Company's intellectual property assets for a limited period of time that is less than the estimated life of the assets. At the same time the Company entered into the current commercial license agreement with SDC, the Company also entered into a new supplemental material purchase agreement with SDC. Under the supplemental material purchase agreement, SDC agrees to purchase from the Company a minimum amount of phosphorescent emitter materials for use in the manufacture of licensed products. This minimum commitment is subject to SDC’s requirements for phosphorescent emitter materials and the Company’s ability to meet these requirements over the term of the supplemental agreement. In 2015, the Company entered into an OLED patent license agreement and an OLED commercial supply agreement with LG Display Co., Ltd. (LG Display) which were effective as of January 1, 2015 and superseded the existing 2007 commercial supply agreement between the parties. The terms of the agreements were set to expire by the end of 2022. The patent license agreement provides LG Display a non-exclusive, royalty bearing portfolio license to make and sell OLED displays under the Company's patent portfolio. The patent license calls for license fees, prepaid royalties and running royalties on licensed products. The agreements include customary provisions relating to warranties, indemnities, confidentiality, assignability and business terms. The agreements provide for certain other minimum obligations relating to the volume of material sales anticipated over the life of the agreements as well as minimum royalty revenue to be generated under the patent license agreement. The Company generates revenue under these agreements that are predominantly tied to LG Display’s sales of OLED licensed products. The OLED commercial supply agreement provides for the sale of materials for use by LG Display, which may include phosphorescent emitters and host materials. In 2021, the Company entered into amendments of the OLED patent license agreement and the OLED commercial supply agreement with LG Display, which were effective as of January 1, 2021. The amended agreements included a term extension and are set to expire by the end of 2025. In 2016, the Company entered into long-term, multi-year OLED patent license and material purchase agreements with Tianma Micro-electronics Co., Ltd. (Tianma). Under the license agreement, the Company has granted Tianma non-exclusive license rights under various patents owned or controlled by the Company to manufacture and sell OLED display products. The license agreement calls for license fees and running royalties on licensed products. Additionally, the Company supplies phosphorescent OLED materials to Tianma for use in its licensed products. In 2017, the Company entered into long-term, multi-year agreements with BOE Technology Group Co., Ltd. (BOE). Under these agreements, the Company has granted BOE non-exclusive license rights under various patents owned or controlled by the Company to manufacture and sell OLED display products. The Company supplies phosphorescent OLED materials to BOE for use in its licensed products. In 2018, the Company entered into long-term, multi-year OLED patent license and material purchase agreements with Visionox Technology, Inc. (Visionox). Under the license agreement, the Company granted certain of Visionox’s affiliates a non-exclusive license rights under various patents owned or controlled by the Company to manufacture and sell OLED display products. The license agreement calls for license fees and running royalties on licensed products. Additionally, the Company supplies phosphorescent OLED materials to Visionox for use in its licensed products. On April 22, 2021, the Company announced that it had extended the Visionox agreement by entering into new five-year In 2019, the Company entered into an evaluation and commercial supply relationship with Wuhan China Star Optoelectronics Semiconductor Display Technology Co., Ltd. (CSOT). In 2020, the Company entered into long-term, multi-year agreements with CSOT. Under these agreements, the Company has granted CSOT non-exclusive license rights under various patents owned or controlled by the Company to manufacture and sell OLED display products. The Company also supplies phosphorescent OLED materials to CSOT for use in its licensed products. All material sales transactions that are not variable consideration transactions are billed and due within 90 days and substantially all are transacted in U.S. dollars.
Cost of Sales	Cost of Sales Cost of sales consists of labor and material costs associated with the production of materials processed at the Company's manufacturing partners and at the Company's internal manufacturing processing facility. The Company’s portion of cost of sales also includes depreciation of manufacturing equipment, as well as manufacturing overhead costs and inventory adjustments for excess and obsolete inventory.
Research and Development	Research and Development Expenditures for research and development are charged to expense as incurred.
Patent Costs	Patent Costs Costs associated with patent applications, patent prosecution, patent defense and the maintenance of patents are charged to expense as incurred. Costs to successfully defend a challenge to a patent are capitalized to the extent of an evident increase in the value of the patent. Costs that relate to an unsuccessful outcome are charged to expense.
Amortization of Acquired Technology	Amortization of Acquired Technology 10 years
Amortization of Other Intangible Assets	Amortization of Other Intangible Assets
Translation of Foreign Currency Financial Statements and Foreign Currency Transactions	Translation of Foreign Currency Financial Statements and Foreign Currency Transactions The Company’s reporting currency is the U.S. dollar. The functional currency for the UDC Ireland subsidiary is also the U.S. dollar and the functional currency for the OMM subsidiary and each of the Company's Asia-Pacific foreign subsidiaries is its local currency. The Company translates the amounts included in the Consolidated Statements of Income from OMM and its Asia-Pacific foreign subsidiaries into U.S. dollars at weighted-average exchange rates, which the Company believes are representative of the actual exchange rates on the dates of the transactions. The Company's foreign subsidiaries' assets and liabilities are translated into U.S. dollars from the local currency at the actual exchange rates as of the end of each reporting date, and the Company records the resulting foreign exchange translation adjustments in the Consolidated Balance Sheets as a component of accumulated other comprehensive loss. The overall effect of the translation of foreign currency and foreign currency transactions to date has been insignificant.
Income Taxes	Income Taxes
Share-Based Payment Awards	Share-Based Payment Awards The Company recognizes in the Consolidated Statements of Income the grant-date fair value of equity-based awards such as shares issued under employee stock purchase plans, restricted stock awards, restricted stock units and performance unit awards issued to employees and directors. The grant-date fair value of stock awards is based on the closing price of the stock on the date of grant. The fair value of share-based awards is recognized as compensation expense on a straight-line basis over the requisite service period, net of forfeitures. The Company issues new shares upon the respective grant, exercise or vesting of the share-based payment awards, as applicable. Performance unit awards are subject to either a performance-based or market-based vesting requirement. For performance-based vesting, the grant-date fair value of the award, based on fair value of the Company's common stock, is recognized over the service period based on an assessment of the likelihood that the applicable performance goals will be achieved and compensation expense is periodically adjusted based on actual and expected performance. Compensation expense for performance unit awards with market-based vesting is calculated based on the estimated fair value as of the grant date utilizing a Monte Carlo simulation model and is recognized over the service period on a straight-line basis.

CASH, CASH EQUIVALENTS AND IN_2

CASH, CASH EQUIVALENTS AND INVESTMENTS (Tables)	3 Months Ended
	Mar. 31, 2021
Cash And Cash Equivalents [Abstract]
Schedule of Cash, Cash Equivalents	The following table provides details regarding the Company’s portfolio of cash and cash equivalents (in thousands): Amortized Unrealized Aggregate Cash and Cash Equivalents Classification Cost Gains (Losses) Market Value March 31, 2021 Cash accounts in banking institutions $ 160,850 $ — $ — $ 160,850 Money market accounts 16,438 — — 16,438 U.S. Government bonds 548,997 — (6 ) 548,991 $ 726,285 $ — $ (6 ) $ 726,279 December 31, 2020 Cash accounts in banking institutions $ 163,779 $ — $ — $ 163,779 Money market accounts 17,261 — — 17,261 U.S. Government bonds 448,970 6 (4 ) 448,972 $ 630,010 $ 6 $ (4 ) $ 630,012
Schedule of Short-Term Investments	The following table provides details regarding the Company’s portfolio of short-term investments (in thousands): Amortized Unrealized Aggregate Short-term Investments Classification Cost Gains (Losses) Market Value March 31, 2021 Certificates of deposit $ 720 $ — $ — $ 720 $ 720 $ — $ — $ 720 December 31, 2020 U.S. Government bonds $ 99,929 $ 67 $ — $ 99,996 $ 99,929 $ 67 $ — $ 99,996

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following table provides the assets and liabilities carried at fair value measured on a recurring basis as of March 31, 2021 (in thousands): Fair Value Measurements, Using Total Carrying Value as of March 31, 2021 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents $ 548,991 $ 548,991 $ — $ — Short-term investments 720 720 — — Convertible notes 500 — — 500 The following table provides the assets and liabilities carried at fair value measured on a recurring basis as of December 31, 2020 (in thousands): Fair Value Measurements, Using Total Carrying Value as of December 31, 2020 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents $ 466,233 $ 466,233 $ — $ — Short-term investments 99,996 99,996 — —

INVENTORY (Tables)

INVENTORY (Tables)	3 Months Ended
	Mar. 31, 2021
Inventory Disclosure [Abstract]
Schedule of Inventory	Inventory consisted of the following (in thousands): March 31, 2021 December 31, 2020 Raw materials $ 60,458 $ 46,843 Work-in-process 2,882 9,904 Finished goods 38,082 34,844 Inventory $ 101,422 $ 91,591

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	3 Months Ended
	Mar. 31, 2021
Property Plant And Equipment [Abstract]
Property and Equipment	Property and equipment, net consist of the following (in thousands): March 31, 2021 December 31, 2020 Land $ 2,642 $ 2,642 Building and improvements 55,321 53,568 Office and lab equipment 91,857 85,881 Furniture, fixtures and computer related assets 11,948 8,921 Construction-in-progress 22,803 23,594 184,571 174,606 Less: Accumulated depreciation (76,756 ) (72,493 ) Property and equipment, net $ 107,815 $ 102,113

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2021
Finite Lived Intangible Assets Net [Abstract]
Schedule of Acquired Technology	These intangible assets consist of the following (in thousands): March 31, 2021 December 31, 2020 PD-LD, Inc. $ 1,481 $ 1,481 Motorola 15,909 15,909 BASF 95,989 95,989 Fujifilm 109,462 109,462 Other 462 462 223,303 223,303 Less: Accumulated amortization (158,197 ) (153,050 ) Acquired technology, net $ 65,106 $ 70,253
Schedule of Other Intangible Assets	At March 31, 2021, these other intangible assets consist of the following (in thousands): March 31, 2021 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Customer relationships $ 10,520 $ (4,284 ) $ 6,236 Developed IP, processes and recipes 4,820 (1,507 ) 3,313 Trade name/Trademarks 1,500 (705 ) 795 Other 297 — 297 Total identifiable other intangible assets $ 17,137 $ (6,496 ) $ 10,641

LEASES (Tables)

LEASES (Tables)	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Summary of Operating Lease Cost and Supplemental Cash Flow Information Related to Operating Leases	The following table presents the Company’s operating lease cost and supplemental cash flow information related to the Company’s operating leases (in thousands): Three Months Ended March 31, 2021 2020 Operating lease cost $ 615 $ 537 Non-cash activity: Right-of-use assets obtained in exchange for lease obligations $ 4,720 $ —
Schedule Of Operating Lease Right of Use Assets and Liabilities	The following table presents the Company’s operating right-of-use assets and liabilities (in thousands): March 31, 2021 December 31, 2020 Right-of-use assets $ 12,819 $ 8,750 Short-term lease liabilities 2,324 1,871 Long-term lease liabilities 10,495 6,879
Schedule of Weighted Average Assumptions Used to Compute Right-of-use Assets and Lease Liabilities	The following table presents weighted average assumptions used to compute the Company’s right-of-use assets and lease liabilities: March 31, 2021 Weighted average remaining lease term (in years) 7.3 Weighted average discount rate 3.4 %
Schedule of Undiscounted Future Minimum Lease Payments Having Non-cancelable Lease Terms	As of March 31, 2021, current operating leases had remaining terms between two and eight years with options to extend the lease terms. Undiscounted future minimum lease payments as of March 31, 2021, by year and in the aggregate, having non-cancelable lease terms in excess of one year were as follows (in thousands): Maturities of Operating Lease Liabilities 2021 (1) $ 1,987 2022 2,541 2023 1,652 2024 1,474 2025 1,263 Thereafter 5,520 Total lease payments 14,437 Less: Imputed interest (1,618 ) Present value of lease payments $ 12,819 (1) Scheduled maturities of lease liabilities represent the time-period of April 1, 2021 to December 31, 2021.

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	3 Months Ended
	Mar. 31, 2021
Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Loss	Amounts related to the changes in accumulated other comprehensive loss were as follows (in thousands): Unrealized Gain (Loss) on Available-for-Sale Securities Net Unrealized Gain (Loss) on Retirement Plan (2) Change in Cumulative Foreign Currency Translation Adjustment Total Affected Line Items in the Consolidated Statements of Income Balance December 31, 2020, net of tax $ 91 $ (36,075 ) $ (35 ) $ (36,019 ) Other comprehensive loss before reclassification (58 ) — (106 ) (164 ) Reclassification to net income (1) — 1,174 — 1,174 Selling, general and administrative, research and development and cost of sales Change during period (58 ) 1,174 (106 ) 1,010 Balance March 31, 2021, net of tax $ 33 $ (34,901 ) $ (141 ) $ (35,009 ) Unrealized Gain (Loss) on Available-for-Sale Securities Net Unrealized Gain (Loss) on Retirement Plan (2) Change in Cumulative Foreign Currency Translation Adjustment Total Affected Line Items in the Consolidated Statements of Income Balance December 31, 2019, net of tax $ 191 $ (17,167 ) $ (21 ) $ (16,997 ) Other comprehensive gain before reclassification 1,855 — (33 ) 1,822 Reclassification to net income (1) — 638 — 638 Selling, general and administrative, research and development and cost of sales Change during period 1,855 638 (33 ) 2,460 Balance March 31, 2020, net of tax $ 2,046 $ (16,529 ) $ (54 ) $ (14,537 ) (1) The Company reclassified amortization of prior service cost and actuarial loss for its retirement plan from accumulated other comprehensive loss to net income of $1.2 million and $638,000 for the three months ended March 31, 2021 and 2020. (2) Refer to Note 14: Supplemental Executive Retirement Plan.

SUPPLEMENTAL EXECUTIVE RETIRE_2

SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN (Tables)	3 Months Ended
	Mar. 31, 2021
Compensation And Retirement Disclosure [Abstract]
Components of Net Periodic Pension Cost	The components of net periodic pension cost were as follows (in thousands): Three Months Ended March 31, 2021 2020 Service cost $ 428 $ 273 Interest cost 291 321 Amortization of prior service cost 275 275 Amortization of loss 1,234 545 Total net periodic benefit cost $ 2,228 $ 1,414

CONCENTRATION OF RISK (Tables)

CONCENTRATION OF RISK (Tables)	3 Months Ended
	Mar. 31, 2021
Risks And Uncertainties [Abstract]
Revenues and Accounts Receivable From Our Largest Customers	Revenues and accounts receivable from the Company's largest customers were as follows (in thousands): % of Total Revenue for the Three Months Ended March 31, Accounts Receivable as of Customer 2021 2020 March 31, 2021 A 36% 41% $ 6,204 B 23% 25% $ 20,769 C 20% 23% $ 22,802 D 12% 7% $ 17,740
Revenues by Geographic Area	Revenues by geographic area are as follows (in thousands): Three Months Ended March 31, Country 2021 2020 South Korea $ 67,975 $ 69,425 China 60,504 37,834 Japan 1,315 1,787 Other non-U.S. locations 825 497 Total non-U.S. locations 130,619 109,543 United States 3,381 2,734 Total revenue $ 134,000 $ 112,277
Long-Lived Assets (Net) by Geographic Area	Long-lived assets (net), by geographic area are as follows (in thousands): March 31, 2021 December 31, 2020 United States $ 99,678 $ 93,230 Other 8,137 8,883 Total long-lived assets $ 107,815 $ 102,113

REVENUE RECOGNITION (Tables)

REVENUE RECOGNITION (Tables)	3 Months Ended
	Mar. 31, 2021
Revenue From Contract With Customer [Abstract]
Schedule of Assets and Liabilities Associated with Contracts from Customers	The following table provides information about assets and liabilities associated with our contracts from customers (in thousands): As of March 31, 2021 Accounts receivable $ 91,327 Short-term unbilled receivables 24,900 Long-term unbilled receivables — Short-term deferred revenue 128,546 Long-term deferred revenue 49,578
Summary of Significant Changes in Unbilled Receivables and Deferred Liabilities Balances	Significant changes in the unbilled receivables and deferred liabilities balances for the three months ended March 31, 2021 and 2020, are as follows (in thousands): Three Months Ended March 31, 2021 Unbilled Receivables Deferred Revenue Balance at December 31, 2020 $ 10,429 $ (162,301 ) Revenue recognized that was previously included in deferred revenue — 33,439 Increases due to cash received — (53,000 ) Cumulative catch-up adjustment arising from changes in estimates of transaction price — 3,738 Unbilled receivables recognized 20,471 — Transferred to receivables from unbilled receivables (6,000 ) — Net change 14,471 (15,823 ) Balance at March 31, 2021 $ 24,900 $ (178,124 ) Three Months Ended March 31, 2020 Unbilled Receivables Deferred Revenue Balance at December 31, 2019 $ 1,362 $ (144,862 ) Revenue recognized that was previously included in deferred revenue — 38,749 Increases due to cash received — (43,685 ) Cumulative catch-up adjustment arising from changes in estimates of transaction price — 367 Unbilled receivables recognized 1,395 — Net change 1,395 (4,569 ) Balance at March 31, 2020 $ 2,757 $ (149,431 )

NET INCOME PER COMMON SHARE (Ta

NET INCOME PER COMMON SHARE (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Schedule of Earnings Per Share	The following table is a reconciliation of net income and the shares used in calculating basic and diluted net income per common share for the three months ended March 31, 2021 and 2020 (in thousands, except share and per share data): Three Months Ended March 31, 2021 2020 Numerator: Net income $ 51,687 $ 38,155 Adjustment for Basic EPS: Earnings allocated to unvested shareholders (358 ) (339 ) Adjusted net income $ 51,329 $ 37,816 Denominator: Weighted average common shares outstanding – Basic 47,267,921 47,093,033 Effect of dilutive shares: Common stock equivalents arising from stock options and ESPP 165 441 Restricted stock awards and units and performance units 61,618 29,355 Weighted average common shares outstanding – Diluted 47,329,704 47,122,829 Net income per common share: Basic $ 1.09 $ 0.80 Diluted $ 1.08 $ 0.80

BUSINESS - Additional Informati

BUSINESS - Additional Information (Details)	Mar. 31, 2021patent
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of patents issued and pending application	5,000

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details)	Apr. 22, 2021	Jun. 28, 2016	Jul. 23, 2012	Mar. 31, 2021
Summary Of Significant Accounting Policies [Line Items]
Recognized income tax positions measured at likelihood of realization description				Recognized income tax positions are measured at the largest amount of which the likelihood of realization is greater than 50%.
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Recognized income tax positions measured at percentage of likelihood of realization				50.00%
Patents [Member] | FUJIFILM [Member]
Summary Of Significant Accounting Policies [Line Items]
OLED patents useful life			10 years	10 years
Patents [Member] | BASF [Member]
Summary Of Significant Accounting Policies [Line Items]
OLED patents useful life		10 years		10 years
Other Intangible Assets [Member] | Adesis, Inc. [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period of acquired intangible assets (in years)				10 years
Other Intangible Assets [Member] | Adesis, Inc. [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period of acquired intangible assets (in years)				15 years
Visionox Hefei Technology Co. Ltd [Member] | Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional agreement duration	5 years

CASH, CASH EQUIVALENTS AND IN_3

CASH, CASH EQUIVALENTS AND INVESTMENTS - Schedule of Cash, Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash And Cash Equivalents [Line Items]
Cash Equivalents, at Carrying Value	$ 726,285	$ 630,010
Cash Equivalents, Gross Unrealized Gains		6
Cash Equivalents, Gross Unrealized Losses	(6)	(4)
Cash and Cash Equivalents, Fair Value Disclosure	726,279	630,012
Cash Accounts in Banking Institutions [Member]
Cash And Cash Equivalents [Line Items]
Cash Equivalents, at Carrying Value	160,850	163,779
Cash and Cash Equivalents, Fair Value Disclosure	160,850	163,779
Money Market Accounts [Member]
Cash And Cash Equivalents [Line Items]
Cash Equivalents, at Carrying Value	16,438	17,261
Cash and Cash Equivalents, Fair Value Disclosure	16,438	17,261
U.S. Government Bonds [Member]
Cash And Cash Equivalents [Line Items]
Cash Equivalents, at Carrying Value	548,997	448,970
Cash Equivalents, Gross Unrealized Gains		6
Cash Equivalents, Gross Unrealized Losses	(6)	(4)
Cash and Cash Equivalents, Fair Value Disclosure	$ 548,991	$ 448,972

CASH, CASH EQUIVALENTS AND IN_4

CASH, CASH EQUIVALENTS AND INVESTMENTS - Schedule of Short-Term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	$ 720	$ 99,929
Available-for-sale Securities, Gross Unrealized Gains		67
Available-for-sale Securities, Fair Value Disclosure	720	99,996
Certificates of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	720
Available-for-sale Securities, Fair Value Disclosure	$ 720
U.S. Government Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		99,929
Available-for-sale Securities, Gross Unrealized Gains		67
Available-for-sale Securities, Fair Value Disclosure		$ 99,996

CASH, CASH EQUIVALENTS AND IN_5

CASH, CASH EQUIVALENTS AND INVESTMENTS - Additional Information (Details)	Mar. 31, 2021USD ($)Investment	Dec. 31, 2020USD ($)
Cash And Cash Equivalents [Line Items]
Number of Minority Investments | Investment	2
Cost Method Minority Investment Carrying Value	$ 8,000,000
Number Of Convertible Note Investments | Investment	1
Available-for-sale Securities, Fair Value Disclosure	$ 720,000	$ 99,996,000
Fair Value, Inputs, Level 3 [Member]
Cash And Cash Equivalents [Line Items]
Available-for-sale Securities, Fair Value Disclosure	$ 500,000

FAIR VALUE MEASUREMENTS - Sched

FAIR VALUE MEASUREMENTS - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 726,279	$ 630,012
Short-term investments	720	99,996
Fair Value, Measurements, Recurring [Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	548,991	466,233
Short-term investments	720	99,996
Convertible notes	500
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	548,991	466,233
Short-term investments	720	$ 99,996
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible notes	$ 500

FAIR VALUE MEASUREMENTS - Addit

FAIR VALUE MEASUREMENTS - Additional Information (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Credit losses on debt investments	$ 0	$ 0

INVENTORY - Schedule of Invento

INVENTORY - Schedule of Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 60,458	$ 46,843
Work-in-process	2,882	9,904
Finished goods	38,082	34,844
Inventory	$ 101,422	$ 91,591

INVENTORY - Additional Informat

INVENTORY - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Inventory Disclosure [Abstract]
Change in inventory reserve	$ 667,000	$ 611,000

PROPERTY AND EQUIPMENT (Details

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 184,571	$ 174,606
Less: Accumulated depreciation	(76,756)	(72,493)
Property and equipment, net	107,815	102,113
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,642	2,642
Building and improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	55,321	53,568
Office and lab equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	91,857	85,881
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	11,948	8,921
Construction-in-progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 22,803	$ 23,594

PROPERTY AND EQUIPMENT - Additi

PROPERTY AND EQUIPMENT - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property Plant And Equipment [Abstract]
Depreciation expense	$ 4,263	$ 3,615

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Schedule of Acquired Technology (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Acquired technology, gross	$ 223,303	$ 223,303
Less: Accumulated amortization	(158,197)	(153,050)
Acquired technology, net	65,106	70,253
PD LD, Inc [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired technology, gross	1,481	1,481
Motorola [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired technology, gross	15,909	15,909
BASF [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired technology, gross	95,989	95,989
FUJIFILM [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired technology, gross	109,462	109,462
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired technology, gross	$ 462	$ 462

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Acquired Technology - Additional Information (Details) € in Millions	Jun. 28, 2016USD ($)patent	Jun. 28, 2016EUR (€)patent	Jul. 23, 2012USD ($)patent	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)
Finite-Lived Intangible Assets [Line Items]
Amortization related to acquired technology				$ 5,488,000	$ 5,490,000
Future amortization expense, 2021				15,500,000
Future amortization expense, 2022				15,800,000
Future amortization expense, 2023				9,700,000
Future amortization expense, 2024				9,600,000
Future amortization expense, 2025				9,600,000
Future amortization expense, thereafter				4,900,000
Patent Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization related to acquired technology				$ 5,100,000	$ 5,100,000
Patents [Member] | FUJIFILM [Member]
Finite-Lived Intangible Assets [Line Items]
Number of patents acquired (more than) | patent			1,200
Assigned value of acquired intangible assets			$ 105,000,000
Cash paid for OLED patents			$ 4,500,000
OLED patents useful life			10 years	10 years
Patents [Member] | BASF [Member]
Finite-Lived Intangible Assets [Line Items]
Number of patents acquired (more than) | patent	500	500
Assigned value of acquired intangible assets	$ 95,800,000	€ 86.8
Cash paid for OLED patents	$ 217,000
OLED patents useful life	10 years	10 years		10 years

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS - Other Intangible Assets - Additional Information (Details) - Adesis, Inc. [Member] - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Other intangible assets acquired	$ 16,800,000
Other intangible assets	17,137,000
Amortization expense related to other intangible assets	341,000	$ 345,000
Future amortization expense of other intangible assets, remainder of fiscal year 2021	1,100,000
Future amortization expense of other intangible assets, fiscal year 2022	1,400,000
Future amortization expense of other intangible assets, fiscal year 2023	1,400,000
Future amortization expense of other intangible assets, fiscal year 2024	1,400,000
Future amortization expense of other intangible assets, fiscal year 2025	1,400,000
Future amortization expense of other intangible assets, thereafter	3,900,000
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets	$ 10,520,000
Weighted average useful life , intangible assets	11 years 6 months
Internally-developed IP, Processes and Recipes [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets	$ 4,820,000
Weighted average useful life , intangible assets	15 years
Trade Name/Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets	$ 1,500,000
Weighted average useful life , intangible assets	10 years

GOODWILL AND INTANGIBLE ASSET_5

GOODWILL AND INTANGIBLE ASSETS - Schedule of Other Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ (6,496)	$ (6,155)
Net Carrying Amount	10,641	$ 10,685
Adesis, Inc. [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	17,137
Accumulated Amortization	(6,496)
Net Carrying Amount	10,641
Customer Relationships [Member] | Adesis, Inc. [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	10,520
Accumulated Amortization	(4,284)
Net Carrying Amount	6,236
Developed IP, Processes and Recipes [Member] | Adesis, Inc. [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,820
Accumulated Amortization	(1,507)
Net Carrying Amount	3,313
Trade Name/Trademarks [Member] | Adesis, Inc. [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,500
Accumulated Amortization	(705)
Net Carrying Amount	795
Other [Member] | Adesis, Inc. [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	297
Net Carrying Amount	$ 297

LEASES- Additional Information

LEASES- Additional Information (Details)	3 Months Ended
	Mar. 31, 2021
Lessee Lease Description [Line Items]
Operating lease description	Current lease agreements do not contain any residual value guarantees or material restrictive covenants. As of March 31, 2021, the Company did not have any finance leases and no additional operating leases that have not yet commenced.
Minimum [Member]
Lessee Lease Description [Line Items]
Operating leases remaining term	2 years
Operating lease, option to extend	true
Maximum [Member]
Lessee Lease Description [Line Items]
Operating leases remaining term	8 years

LEASES - Summary of Operating L

LEASES - Summary of Operating Lease Cost and Supplemental Cash Flow Information Related to Operating Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Operating lease cost	$ 615	$ 537
Non-cash activity:
Right-of-use assets obtained in exchange for lease obligations	$ 4,720

LEASES - Schedule Of Operating

LEASES - Schedule Of Operating Lease Right of Use Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Lessee Lease Description [Line Items]
Right-of-use assets	$ 12,819	$ 8,750
Current Liabilities [Member]
Lessee Lease Description [Line Items]
Short-term lease liabilities	2,324	1,871
Non-current Liabilities [Member]
Lessee Lease Description [Line Items]
Long-term lease liabilities	$ 10,495	$ 6,879

LEASES - Schedule of Weighted A

LEASES - Schedule of Weighted Average Assumptions Used to Compute Right-of-use Assets and Lease Liabilities (Details)	Mar. 31, 2021
Leases [Abstract]
Weighted average remaining lease term (in years)	7 years 3 months 18 days
Weighted average discount rate	3.40%

LEASES - Schedule of Undiscount

LEASES - Schedule of Undiscounted Future Minimum Lease Payments Having Non-cancelable Lease Terms (Details) $ in Thousands	Mar. 31, 2021USD ($)
Lessee Lease Description [Line Items]
2021	$ 1,987	[1]
2022	2,541
2023	1,652
2024	1,474
2025	1,263
Thereafter	5,520
Total lease payments	14,437
Less: Imputed interest	(1,618)
Other Liabilities [Member]
Lessee Lease Description [Line Items]
Present value of lease payments	$ 12,819
[1]	Scheduled maturities of lease liabilities represent the time-period of April 1, 2021 to December 31, 2021.

RESEARCH AND LICENSE AGREEMEN_2

RESEARCH AND LICENSE AGREEMENTS WITH PRINCETON UNIVERSITY, UNIVERSITY OF SOUTHERN CALIFORNIA AND THE UNIVERSITY OF MICHIGAN - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Royalty expense	$ 112,000	$ 3,284,000
1997 Amended License Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Royalty expense	$ 112,000,000	3,300,000
Royalty rate for licensed products sold by the Company (in hundredths)	3.00%
Royalty rate for licensed products sold by the Company's sublicenses (in hundredths)	3.00%
2006 Research Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research agreement, extension term (in years)	2 years
Research agreement, new amendment expiration date	Apr. 30, 2023
Maximum obligation	$ 6,600,000
Research and development expense incurred	$ 285,000	$ 272,000

EQUITY AND CASH COMPENSATION _2

EQUITY AND CASH COMPENSATION UNDER THE PPG AGREEMENTS - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Long-term Purchase Commitment [Line Items]
Percent of services payable in cash or shares	50.00%
Issuance of common stock in connection with materials and license agreements (in shares)	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	$ 1.5	$ 473,000
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	$ 20	$ 20

SHAREHOLDERS' EQUITY - Addition

SHAREHOLDERS' EQUITY - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	May 04, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Class Of Stock [Line Items]
Preferred Stock, shares authorized ( in shares)		5,000,000		5,000,000
Preferred Stock, par value (in dollars per share)		$ 0.01		$ 0.01
Common Stock, shares authorized (in shares)		200,000,000		200,000,000
Common Stock, par value (in dollars per share)		$ 0.01		$ 0.01
Common Stock, shares issued (in shares)		49,050,776		49,013,476
Common Stock, shares outstanding (in shares)		47,685,128		47,647,828
Treasury stock repurchased shares		0	0
Common stock dividends declared per share		$ 0.20	$ 0.15
Common stock dividends paid per share		$ 0.20
Common stock dividends paid		$ 9.5
Subsequent Event [Member]
Class Of Stock [Line Items]
Common stock dividends declared per share	$ 0.20
Dividend declared date	May 4, 2021
Dividend payable date	Jun. 30, 2021
Dividend record date	Jun. 15, 2021
Series A Nonconvertible Preferred Stock [Member]
Class Of Stock [Line Items]
Preferred Stock, shares issued (in shares)		200,000		200,000
Preferred Stock, shares outstanding (in shares)		200,000		200,000

SHAREHOLDERS' EQUITY - Deferred

SHAREHOLDERS' EQUITY - Deferred Compensation Arrangement - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Non-Employee Members of Scientific Advisory Board [Member]
Deferred Compensation Arrangement with Employees and Non-Employees, Share-Based Payments [Line Items]
Shares issued (in shares)	1,400	1,926
Members of Scientific Advisory Board [Member]
Deferred Compensation Arrangement with Employees and Non-Employees, Share-Based Payments [Line Items]
Fair value of shares issued	$ 300,000	$ 300,000

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Accumulated Other Comprehensive Loss (Details) - USD ($)		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
BALANCE		$ 912,714,000	$ 811,449,000
Other comprehensive gain (loss) before reclassification		(164,000)	1,822,000
Reclassification to net income	[1]	1,174,000	638,000
TOTAL OTHER COMPREHENSIVE INCOME		1,010,000	2,460,000
BALANCE		952,468,000	846,697,000
Unrealized gain (loss) on available-for-sale securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
BALANCE		91,000	191,000
Other comprehensive gain (loss) before reclassification		(58,000)	1,855,000
TOTAL OTHER COMPREHENSIVE INCOME		(58,000)	1,855,000
BALANCE		33,000	2,046,000
Net unrealized gain (loss) on retirement plan [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
BALANCE	[2]	(36,075,000)	(17,167,000)
Reclassification to net income	[1],[2]	1,174,000	638,000
TOTAL OTHER COMPREHENSIVE INCOME	[2]	1,174,000	638,000
BALANCE	[2]	(34,901,000)	(16,529,000)
Change in cumulative foreign currency translation adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
BALANCE		(35,000)	(21,000)
Other comprehensive gain (loss) before reclassification		(106,000)	(33,000)
TOTAL OTHER COMPREHENSIVE INCOME		(106,000)	(33,000)
BALANCE		(141,000)	(54,000)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
BALANCE		(36,019,000)	(16,997,000)
TOTAL OTHER COMPREHENSIVE INCOME		1,010,000	2,460,000
BALANCE		$ (35,009,000)	$ (14,537,000)
[1]	The Company reclassified amortization of prior service cost and actuarial loss for its retirement plan from accumulated other comprehensive loss to net income of $1.2 million and $638,000 for the three months ended March 31, 2021 and 2020.
[2]	Refer to Note 14: Supplemental Executive Retirement Plan

ACCUMULATED OTHER COMPREHENSI_4

ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Accumulated Other Comprehensive Loss (Parenthetical) (Details) - USD ($)		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]
Reclassification to net income	[1]	$ 1,174,000	$ 638,000
[1]	The Company reclassified amortization of prior service cost and actuarial loss for its retirement plan from accumulated other comprehensive loss to net income of $1.2 million and $638,000 for the three months ended March 31, 2021 and 2020.

STOCK-BASED COMPENSATION - Equi

STOCK-BASED COMPENSATION - Equity Compensation Plan - Additional Information (Details) - Equity Compensation Plan [Member]	3 Months Ended
	Mar. 31, 2021shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)	10,500,000
Number of shares available for grant (in shares)	1,828,661
Compensation plan extended term description	Extended the term of the plan through 2024
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration term (in years)	10 years

STOCK-BASED COMPENSATION - Eq_2

STOCK-BASED COMPENSATION - Equity Instruments Other Than Options - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares withheld for tax withholding obligations	$ 9,634,000	$ 4,816,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (shares)	100,079
Total fair value of performance unit awards granted	$ 22,700,000
Shares withheld for tax withholding obligations (in shares)	48,824	24,474
Fair value of shares withheld for tax withholding obligations	$ 9,400,000	$ 3,900,000
Restricted Stock [Member] | Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	3,600,000	3,300,000
Restricted Stock [Member] | Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	1,200,000	877,000
Restricted Stock [Member] | Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 557,000	400,000
Restricted Stock [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock awards and units vesting terms	3 years
Restricted Stock [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock awards and units vesting terms	5 years
Restricted Stock Units (RSUs) [Member] | Research and Development Expense [Member] | Non Employee Members of Scientific Advisory Board [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 36,000	$ 43,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (shares)	69,586
Total fair value of performance unit awards granted	$ 15,800,000
Shares withheld for tax withholding obligations (in shares)	1,224	5,963
Fair value of shares withheld for tax withholding obligations	$ 231,000	$ 930,000
Performance Shares [Member] | Performance-Based Vesting Requirement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (shares)	34,791
Performance Shares [Member] | Market-Based Vesting Requirement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (shares)	34,795
Performance Shares [Member] | Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 211,000	811,000
Performance Shares [Member] | Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	56,000	202,000
Performance Shares [Member] | Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 35,000	$ 113,000

STOCK-BASED COMPENSATION - Boar

STOCK-BASED COMPENSATION - Board of Directors Compensation - Additional Information (Details) - Director [Member] - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Restricted stock awards and units vesting terms	1 year
Fair value of shares issued	$ 294,000	$ 297,000
Shares issued (in shares)	1,353	1,614

STOCK-BASED COMPENSATION - Empl

STOCK-BASED COMPENSATION - Employee Stock Purchase Plan - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Jun. 25, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from common stock issued	$ 432,000	$ 328,000
Employee Stock Purchase Plan (ESPP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for issuance (in shares)			1,000,000
Purchase period (in months)	three-month
Percentage of market value (in hundredths)	85.00%
Maximum allocation of base compensation (in hundredths)	10.00%
Maximum shares per purchase date (in shares)	12,500
Maximum value per calendar year, per employee	$ 25,000
Common stock issued (in shares)	1,782	2,315
Proceeds from common stock issued	$ 348,000	$ 259,000
Employee Stock Purchase Plan (ESPP) [Member] | Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Charges to expense	23,000	22,000
Employee Stock Purchase Plan (ESPP) [Member] | Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Charges to expense	36,000	28,000
Employee Stock Purchase Plan (ESPP) [Member] | Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Charges to expense	$ 25,000	$ 19,000

SUPPLEMENTAL EXECUTIVE RETIRE_3

SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN - Additional Information (Details)	Mar. 31, 2021participant
Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of participants	7

SUPPLEMENTAL EXECUTIVE RETIRE_4

SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN - Components of Net Periodic Pension Cost (Details) - Supplemental Executive Retirement Plan [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Components of net periodic pension cost [Abstract]
Service cost	$ 428	$ 273
Interest cost	291	321
Amortization of prior service cost	275	275
Amortization of loss	1,234	545
Total net periodic benefit cost	$ 2,228	$ 1,414

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Additional Information (Details)	Mar. 31, 2021USD ($)executive_officerEmployeemultiple	Dec. 31, 2020USD ($)
Loss Contingencies [Line Items]
Purchase commitments for inventory | $	$ 18,900,000	$ 13,700,000
Commitment With Executive Officers [Member]
Loss Contingencies [Line Items]
Number of executive officers under agreement | executive_officer	6
Number of senior level employees under agreement | Employee	12
Multiple of sum of average annual base salary and bonus agreement terms	2
Commitment With Senior Level Employees [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Multiple of sum of average annual base salary and bonus agreement terms	1
Commitment With Senior Level Employees [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Multiple of sum of average annual base salary and bonus agreement terms	2

CONCENTRATION OF RISK - Revenue

CONCENTRATION OF RISK - Revenues and Accounts Receivable From Our Largest Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Concentration Risk [Line Items]
Accounts Receivable	$ 91,327		$ 82,261
Total Revenue [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
% of Total Revenue	12.00%	7.00%
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Accounts Receivable	$ 17,740
Major Customer A [Member] | Total Revenue [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
% of Total Revenue	36.00%	41.00%
Major Customer A [Member] | Accounts Receivable [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Accounts Receivable	$ 6,204
Major Customer B [Member] | Total Revenue [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
% of Total Revenue	23.00%	25.00%
Major Customer B [Member] | Accounts Receivable [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Accounts Receivable	$ 20,769
Major Customer C [Member] | Total Revenue [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
% of Total Revenue	20.00%	23.00%
Major Customer C [Member] | Accounts Receivable [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Accounts Receivable	$ 22,802

CONCENTRATION OF RISK - Additio

CONCENTRATION OF RISK - Additional Information (Details) - supplier	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Supplier Concentration Risk [Member]
Concentration Risk [Line Items]
Number of suppliers from which chemical materials were purchased	1
Total Revenue [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage (less than 1% for contracts with U.S. government agencies)	12.00%	7.00%
Excluding North America [Member] | Total Revenue [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage (less than 1% for contracts with U.S. government agencies)	97.00%	98.00%

CONCENTRATION OF RISK - Reven_2

CONCENTRATION OF RISK - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Concentration Risk [Line Items]
Revenues	$ 134,000	$ 112,277
South Korea [Member]
Concentration Risk [Line Items]
Revenues	67,975	69,425
China [Member]
Concentration Risk [Line Items]
Revenues	60,504	37,834
Japan [Member]
Concentration Risk [Line Items]
Revenues	1,315	1,787
Other Non-U.S. Locations [Member]
Concentration Risk [Line Items]
Revenues	825	497
Total Non-U.S. Locations [Member]
Concentration Risk [Line Items]
Revenues	130,619	109,543
United States [Member]
Concentration Risk [Line Items]
Revenues	$ 3,381	$ 2,734

CONCENTRATION OF RISK - Long-Li

CONCENTRATION OF RISK - Long-Lived Assets (Net) by Geographic Area (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total long-lived assets	$ 107,815	$ 102,113
United States [Member]
Segment Reporting Information [Line Items]
Total long-lived assets	99,678	93,230
Other [Member]
Segment Reporting Information [Line Items]
Total long-lived assets	$ 8,137	$ 8,883

INCOME TAXES - Additional Infor

INCOME TAXES - Additional Information (Details) - USD ($) $ in Thousands	Oct. 30, 2018	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2018
Income Taxes [Line Items]
Effective income tax rate (benefit) expense, percent		18.90%	18.60%
Income tax expense (benefit)		$ 12,063	$ 8,700
Long-term asset		$ 106,704		$ 103,341
Withholding and interest for licencing and royalty payments	$ 13,200
Withholding and interest for licencing and royalty payments period	3 years
State and foreign income tax returns subject to examination period minimum (in years)		3 years
State and foreign income tax returns subject to examination period maximum (in years)		4 years
Reduction of Korean Withholding Taxes [Member]
Income Taxes [Line Items]
Reduction of deferred tax asset for foreign tax credits and R&D		$ 20,700		20,700
U.S.Federal Government [Member]
Income Taxes [Line Items]
Estimated settlement amounts due (refunds) from withholding taxes					$ 16,200
Korean Government [Member]
Income Taxes [Line Items]
Estimated settlement amounts due (refunds) from withholding taxes					$ (36,900)
Allocation of Withholding to Non-Korean Patents [Member]
Income Taxes [Line Items]
Long-term asset		43,400		40,100
Allocation of Withholding to Non-Korean Patents [Member] | U.S.Federal Government [Member]
Income Taxes [Line Items]
Estimated settlement amounts due (refunds) from withholding taxes		$ 35,900		$ 32,700

REVENUE RECOGNITION - Additiona

REVENUE RECOGNITION - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation Of Revenue [Line Items]
Backlog associated with committed purchase orders from customers	$ 19.4
Revenue from Contracts with Customers - ASU No. 2014-09 [Member]
Disaggregation Of Revenue [Line Items]
Percentage of revenue recorded from sales of materials	98.00%	98.00%
Revenue from Contracts with Customers - ASU No. 2014-09 [Member] | Adesis, Inc. [Member]
Disaggregation Of Revenue [Line Items]
Percentage of revenue recorded from provision of services	2.00%	2.00%

REVENUE RECOGNITION - Schedule

REVENUE RECOGNITION - Schedule of Assets and Liabilities Associated with Contracts from Customers (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Disaggregation Of Revenue [Line Items]
Accounts receivable	$ 91,327	$ 82,261
Short-term deferred revenue	128,546	105,215
Long-term deferred revenue	49,578	$ 57,086
Other Current Assets [Member]
Disaggregation Of Revenue [Line Items]
Short-term unbilled receivables	$ 24,900

REVENUE RECOGNITION - Summary o

REVENUE RECOGNITION - Summary of Significant Changes in Unbilled Receivables and Deferred Liabilities Balances (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Deferred Revenue (Increase) Decrease
Balance at December 31, 2020	$ (162,301)	$ (144,862)
Revenue recognized that was previously included in deferred revenue	33,439	38,749
Increases due to cash received	(53,000)	(43,685)
Cumulative catch-up adjustment arising from changes in estimates of transaction price	3,738	367
Net change	(15,823)	(4,569)
Balance at March 31, 2021	(178,124)	(149,431)
Unbilled Receivables Increase (Decrease)
Balance at December 31, 2020	10,429	1,362
Unbilled receivables recognized	20,471	1,395
Transferred to receivables from unbilled receivables	(6,000)
Net change	14,471	1,395
Balance at March 31, 2021	$ 24,900	$ 2,757

NET INCOME PER COMMON SHARE - S

NET INCOME PER COMMON SHARE - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net income	$ 51,687	$ 38,155
Adjustment for Basic EPS:
Earnings allocated to unvested shareholders	(358)	(339)
Adjusted net income	$ 51,329	$ 37,816
Denominator:
Weighted average common shares outstanding – Basic	47,267,921	47,093,033
Effect of dilutive shares:
Common stock equivalents arising from stock options and ESPP	165	441
Restricted stock awards and units and performance units	61,618	29,355
Weighted average common shares outstanding – Diluted	47,329,704	47,122,829
Basic	$ 1.09	$ 0.80
Diluted	$ 1.08	$ 0.80

NET INCOME PER COMMON SHARE - A

NET INCOME PER COMMON SHARE - Additional Information (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Antidilutive securities excluded from calculation of diluted EPS	0	14,112