Power Integrations (POWI) 10-K 7 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($) $ / shares in Units, $ in Billions	12 Months Ended
	Dec. 31, 2019	Feb. 03, 2020	Jun. 28, 2019
Document Information [Line Items]
Title of 12(b) Security	Common Stock
Entity Address, Address Line One	5245 Hellyer Avenue
Entity Incorporation, State or Country Code	DE
Entity Registrant Name	POWER INTEGRATIONS, INC.
Entity Central Index Key	0000833640
Current Fiscal Year End Date	--12-31
Trading Symbol	POWI
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	000-23441
Document Fiscal Year Focus	2019
Amendment Flag	false
Document Fiscal Period Focus	FY
Entity Listing, Par Value Per Share	$ 0.01
Entity Common Stock, Shares Outstanding		29,538,300
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Small Business	false
Entity Public Float			$ 1.7
Entity Tax Identification Number	94-3065014
City Area Code	408
Local Phone Number	414-9200
Entity Address, City or Town	San Jose
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95138-1002
Security Exchange Name	NASDAQ

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 178,690	$ 134,137
Short-term marketable securities	232,398	94,451
Accounts receivable, net of allowance for doubtful accounts of $763 and $706 in 2019 and 2018, respectively	24,274	11,072
Inventories	90,380	80,857
Prepaid expenses and other current assets	15,597	11,915
Total current assets	541,339	332,432
PROPERTY AND EQUIPMENT, net	116,619	114,117
INTANGIBLE ASSETS, net	16,865	21,152
GOODWILL	91,849	91,849
DEFERRED TAX ASSETS	2,836	6,906
OTHER ASSETS	34,388	22,241
Total assets	803,896	588,697
CURRENT LIABILITIES:
Accounts payable	27,433	31,552
Accrued payroll and related expenses	13,408	12,131
Taxes payable	584	933
Other accrued liabilities	9,051	3,750
Total current liabilities	50,476	48,366
LONG-TERM INCOME TAXES PAYABLE	14,617	8,652
DEFERRED TAX LIABILITIES	164	216
OTHER LIABILITIES	14,093	4,391
Total liabilities	79,350	61,625
STOCKHOLDERS’ EQUITY:
Common stock, $0.001 par value Authorized - 140,000,000 shares Outstanding - 29,430,962 and 28,888,643 shares in 2019 and 2018, respectively	28	28
Additional paid-in capital	152,117	126,164
Accumulated other comprehensive loss	(3,130)	(1,689)
Retained earnings	575,531	402,569
Total stockholders’ equity	724,546	527,072
Total liabilities and stockholders’ equity	$ 803,896	$ 588,697

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, allowance	$ 763	$ 706
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	140,000,000	140,000,000
Common stock, shares outstanding	29,430,962	28,888,643

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
NET REVENUES		$ 420,669	$ 415,955	$ 431,755
COST OF REVENUES		207,267	201,167	218,091
GROSS PROFIT		213,402	214,788	213,664
OPERATING EXPENSES:
Research and development		73,470	70,580	68,501
Sales and marketing		54,297	53,064	51,384
General and administrative		37,582	35,496	36,142
Litigation settlement		(168,969)	0	0
Total operating expenses		(3,620)	159,140	156,027
INCOME FROM OPERATIONS		217,022	55,648	57,637
OTHER INCOME		5,392	4,116	2,662
INCOME BEFORE INCOME TAXES		222,414	59,764	60,299
PROVISION (BENEFIT) FOR INCOME TAXES		28,946	(10,220)	32,690
NET INCOME		$ 193,468	$ 69,984	$ 27,609
EARNINGS PER SHARE:
Basic		$ 6.61	$ 2.38	$ 0.93
Diluted	[1]	$ 6.49	$ 2.32	$ 0.90
SHARES USED IN PER SHARE CALCULATION:
Basic		29,267	29,456	29,674
Diluted	[1]	29,816	30,147	30,545
[1]	The Company includes the shares underlying performance-based awards in the calculation of diluted earnings per share if the performance conditions have been satisfied as of the end of the reporting period and excludes such shares when the necessary conditions have not been met. The Company has included in the 2019, 2018 and 2017 calculations those shares that were contingently issuable upon the satisfaction of the performance conditions as of the end of the respective periods.

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 193,468	$ 69,984	$ 27,609
Other comprehensive income:
Foreign currency translation adjustments, net of $0 tax in 2019, 2018 and 2017	(518)	(236)	79
Unrealized gain (loss) on marketable securities, net of $0 tax in 2019, 2018 and 2017	849	161	(207)
Unrealized actuarial gain (loss) on pension benefits, net of tax of $497, ($144), and ($194) in 2019, 2018 and 2017, respectively	(1,772)	525	699
Total other comprehensive income (loss)	(1,441)	450	571
Total comprehensive income	192,027	70,434	28,180
Foreign currency translation adjustment, tax	0	0	0
Unrealized gain on marketable securities, tax	0	0	0
Unrealized actuarial gain (loss) on pension benefits, tax	$ (144)	$ (198)	$ 98

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | ASU 2016-09	$ 7,542				$ 7,542
Beginning Balance (in shares) at Dec. 31, 2016		29,250
Beginning Balance at Dec. 31, 2016	503,084	$ 28	$ 172,875	$ (2,710)	332,891
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock award plans (in shares)		569
Issuance of common stock under employee stock option and stock award plans		$ 1
Issuance of common stock under employee stock option and stock award plans	5,087		5,086
Repurchase of common stock (in shares)		(129)
Repurchase of common stock	(9,188)		(9,188)
Issuance of common stock under employee stock purchase plan (in shares)		92
Issuance of common stock under employee stock purchase plan	4,934		4,934
Stock-based compensation expense related to employee stock options and awards	23,337		23,337
Stock-based compensation expense related to employee stock purchases	1,340		1,340
Payment of dividends to stockholders	(16,634)				(16,634)
Unrealized actuarial gain (loss) on pension benefits	699			699
Unrealized gain (loss) on marketable securities,	(207)			(207)
Translation adjustment	79			79
Net income (loss)	27,609				27,609
Ending Balance (in shares) at Dec. 31, 2017		29,782
Ending Balance at Dec. 31, 2017	547,682	$ 29	198,384	(2,139)	351,408
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock award plans (in shares)		591
Issuance of common stock under employee stock option and stock award plans	4,010		4,010
Repurchase of common stock (in shares)		(1,572)
Repurchase of common stock	(103,154)	$ (1)	(103,153)
Issuance of common stock under employee stock purchase plan (in shares)		88
Issuance of common stock under employee stock purchase plan	5,343		5,343
Stock-based compensation expense related to employee stock options and awards	20,027		20,027
Stock-based compensation expense related to employee stock purchases	1,553		1,553
Payment of dividends to stockholders	(18,823)				(18,823)
Unrealized actuarial gain (loss) on pension benefits	525			525
Unrealized gain (loss) on marketable securities,	161			161
Translation adjustment	(236)			(236)
Net income (loss)	69,984				69,984
Ending Balance (in shares) at Dec. 31, 2018		28,889
Ending Balance at Dec. 31, 2018	527,072	$ 28	126,164	(1,689)	402,569
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock award plans (in shares)		565
Issuance of common stock under employee stock option and stock award plans	4,359		4,359
Repurchase of common stock (in shares)		(121)
Repurchase of common stock	(7,302)		(7,302)
Issuance of common stock under employee stock purchase plan (in shares)		98
Issuance of common stock under employee stock purchase plan	5,549		5,549
Stock-based compensation expense related to employee stock options and awards	21,686		21,686
Stock-based compensation expense related to employee stock purchases	1,661		1,661
Payment of dividends to stockholders	(20,506)				(20,506)
Unrealized actuarial gain (loss) on pension benefits	(1,772)			(1,772)
Unrealized gain (loss) on marketable securities,	849			849
Translation adjustment	(518)			(518)
Net income (loss)	193,468				193,468
Ending Balance (in shares) at Dec. 31, 2019		29,431
Ending Balance at Dec. 31, 2019	$ 724,546	$ 28	$ 152,117	$ (3,130)	$ 575,531

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 193,468	$ 69,984	$ 27,609
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	19,190	18,918	18,374
Amortization of intangibles	5,213	5,267	6,083
Loss on disposal of property and equipment	249	553	360
Stock-based compensation expense	23,347	21,580	24,677
Amortization of premium (accretion of discount) on marketable securities	(192)	227	1,100
Deferred income taxes	4,019	(4,465)	15,838
Increase (decrease) in accounts receivable allowances	57	(28)	209
Change in operating assets and liabilities:
Accounts receivable	(13,259)	5,754	(10,479)
Inventories	(9,523)	(23,770)	(4,523)
Prepaid expenses and other assets	(2,132)	(1,495)	(17,646)
Accounts payable	(6,556)	1,336	396
Taxes payable and accrued liabilities	10,618	(9,897)	20,041
Net cash provided by operating activities	224,499	83,964	82,039
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(24,114)	(24,677)	(32,496)
Acquisition of technology licenses	(1,026)	(900)	0
Purchases of marketable securities	(207,240)	(62,833)	(151,663)
Proceeds from sales and maturities of marketable securities	70,334	157,551	149,443
Net cash provided by (used in) investing activities	(162,046)	69,141	(34,716)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock under employee stock plans	9,908	9,353	10,020
Repurchase of common stock	(7,302)	(103,153)	(9,188)
Payments of dividends to stockholders	(20,506)	(18,823)	(16,634)
Proceeds from draw on line of credit	0	8,000	5,000
Payments on line of credit	0	(8,000)	(5,000)
Net cash used in financing activities	(17,900)	(112,623)	(15,802)
NET INCREASE IN CASH AND CASH EQUIVALENTS	44,553	40,482	31,521
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	134,137	93,655	62,134
CASH AND CASH EQUIVALENTS AT END OF PERIOD	178,690	134,137	93,655
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Unpaid property and equipment	4,355	1,818	4,913
Unpaid technology licenses	0	100	0
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid (refund) for income taxes, net of refunds (Note 11)	$ 21,327	$ 7,437	$ (1,571)

THE COMPANY

THE COMPANY	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
THE COMPANY [Text Block]	THE COMPANY:

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUTING POLICIES [Text Block]	SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS: Significant Accounting Policies and Estimates Segment Reporting The Company is organized and operates as one reportable segment, the design, development, manufacture and marketing of integrated circuits and related components for use primarily in the high-voltage power conversion markets. The Company’s chief operating decision maker, the Chief Executive Officer, reviews financial information presented on a consolidated basis for purposes of making operating decisions and assessing financial performance. Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries after elimination of all intercompany transactions and balances. 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 disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. On an ongoing basis, the Company evaluates its estimates, including those related to revenue recognition and allowances for receivables and inventories. These estimates are based on historical facts and various other factors, which the Company believes to be reasonable at the time the estimates are made. However, as the effects of future events cannot be determined with precision, actual results could differ significantly from management’s estimates. Revenue Recognition The Company applies the provisions of Accounting Standards Codification (ASC) 606-10, Revenue from Contracts with Customers , and all related appropriate guidance. The Company recognizes revenue under the core principle to depict the transfer of control to the Company’s customers in an amount reflecting the consideration the Company expects to be entitled. In order to achieve that core principle, the Company applies the following five-step approach: (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when a performance obligation is satisfied. Product revenues consist of sales to original equipment manufacturers, or OEMs, merchant power supply manufacturers and distributors. The Company considers customer purchase orders, which in some cases are governed by master sales agreements, to be the contracts with a customer. In situations where sales are to a distributor, the Company has concluded that its contracts are with the distributor as the Company holds a contract bearing enforceable rights and obligations only with the distributor. As part of its consideration of the contract, the Company evaluates certain factors including the customer’s ability to pay (or credit risk). For each contract, the Company considers the promise to transfer products, each of which is distinct, to be the identified performance obligations. In determining the transaction price the Company evaluates whether the price is subject to refund or adjustment to determine the net consideration to which the Company expects to be entitled. As the Company’s standard payment terms are less than one year, the Company has elected the practical expedient under ASC 606-10-32-18 to not assess whether a contract has a significant financing component. The Company allocates the transaction price to each distinct product based on their relative standalone selling price. The product price as specified on the purchase order is considered the standalone selling price as it is an observable input which depicts the price as if sold to a similar customer in similar circumstances. Revenue is recognized when control of the product is transferred to the customer (i.e., when the Company’s performance obligation is satisfied), which typically occurs at shipment. Further, in determining whether control has transferred, the Company considers if there is a present right to payment and legal title, along with risks and rewards of ownership having transferred to the customer. Frequently, the Company receives orders for products to be delivered over multiple dates that may extend across several reporting periods. The Company invoices for each delivery upon shipment and recognizes revenues for each distinct product delivered, assuming transfer of control has occurred. As scheduled delivery dates are within one year, under the optional exemption provided by ASC 606-10-50-14 revenues allocated to future shipments of partially completed contracts are not disclosed. The Company has also elected the practical expedient under ASC 340-40-25-4 to expense commissions when incurred as the amortization period of the commission asset the Company would have otherwise recognized is less than one year. Sales to international customers that are shipped from the Company’s facility outside of the United States are pursuant to EX Works, or EXW, shipping terms, meaning that control of the product transfers to the customer upon shipment from the Company’s foreign warehouse. Sales to international customers that are shipped from the Company’s facility in California are pursuant to Delivered at Frontier, or DAF, shipping terms. As such, control of the product passes to the customer when the shipment reaches the destination country and revenue is recognized upon the arrival of the product in that country. Shipments to customers in the Americas are pursuant to Free on Board, or FOB, point of origin shipping terms meaning that control is passed to the customer upon shipment. Sales to most distributors are made under terms allowing certain price adjustments and limited rights of return (known as “stock rotation”) of the Company’s products held in their inventory or upon sale to their end customers. Revenue from sales to distributors is recognized upon the transfer of control to the distributor. Frequently, distributors need to sell at a price lower than the standard distribution price in order to win business. At the time the distributor invoices its customer or soon thereafter, the distributor submits a “ship and debit” price adjustment claim to the Company to adjust the distributor’s cost from the standard price to the pre-approved lower price. After the Company verifies that the claim was pre-approved, a credit memo is issued to the distributor for the ship and debit claim. In determining the transaction price, the Company considers ship and debit price adjustments to be variable consideration. Such price adjustments are estimated using the expected value method based on an analysis of actual ship and debit claims, at the distributor and product level, over a period of time considered adequate to account for current pricing and business trends. Historically, actual price adjustments for ship and debit claims relative to those estimated and included when determining the transaction price have not materially differed. Stock rotation rights grant the distributor the ability to return certain specified amounts of inventory. Stock rotation adjustments are an additional form of variable consideration and are also estimated using the expected value method based on historical return rates. Historically, distributor stock rotation adjustments have not been material. Sales to certain distributors are made under terms that do not include rights of return or price concessions after the product is shipped to the distributor. Accordingly, upon application of steps one through five above, product revenue is recognized upon shipment and transfer of control. The Company generally provides an assurance warranty that its products will substantially conform to the published specifications for twelve months from the date of shipment. The Company’s liability is limited to either a credit equal to the purchase price or replacement of the defective part. Returns under warranty have historically been immaterial. As such, the Company does not record a specific warranty reserve or consider activities related to such warranty, if any, to be a separate performance obligation. Inventories Inventories (which consist of costs associated with the purchases of wafers from domestic and offshore foundries and of packaged components from offshore assembly manufacturers, as well as internal labor and overhead associated with the testing of both wafers and packaged components) are stated at the lower of cost (first-in, first-out) or market. Provisions, when required, are made to reduce excess and obsolete inventories to their estimated net realizable values. Income Taxes Income-tax expense is an estimate of current income taxes payable or refundable in the current fiscal year based on reported income before income taxes. Deferred income taxes reflect the effect of temporary differences and carry-forwards that are recognized for financial reporting and income tax purposes. The Company accounts for income taxes under the provisions of ASC 740, Income Taxe s. Under the provisions of ASC 740, deferred tax assets and liabilities are recognized based on the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, utilizing the tax rates that are expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company recognizes valuation allowances to reduce any deferred tax assets to the amount that it estimates will more likely than not be realized based on available evidence and management’s judgment. The Company limits the deferred tax assets recognized related to certain officers’ compensation to amounts that it estimates will be deductible in future periods based upon Internal Revenue Code Section 162(m). In the event that the Company determines, based on available evidence and management judgment, that all or part of the net deferred tax assets will not be realized in the future, it would record a valuation allowance in the period the determination is made. In addition, the calculation of tax liabilities involves significant judgment in estimating the impact of uncertainties in the application of complex tax laws. Resolution of these uncertainties in a manner inconsistent with the Company’s expectations could have a material impact on the Company’s results of operations and financial position. Business Combinations The purchase price of an acquisition is allocated to the underlying assets acquired and liabilities assumed based upon their estimated fair values at the date of acquisition. To the extent the purchase price exceeds the fair value of the net identifiable tangible and intangible assets acquired and liabilities assumed, such excess is allocated to goodwill. The Company determines the estimated fair values after review and consideration of relevant information, including discounted cash flows, quoted market prices and estimates made by management. The Company adjusts the preliminary purchase price allocation, as necessary, during the measurement period of up to one year after the acquisition closing date as it obtains more information as to facts and circumstances existing at the acquisition date impacting asset valuations and liabilities assumed. Acquisition-related costs are recognized separately from the acquisition and are expensed as incurred. Goodwill and Intangible Assets Goodwill and the Company's domain name are evaluated in accordance with ASC 350-10, Goodwill and Other Intangible Assets, and an impairment analysis is conducted on an annual basis, or sooner if indicators exist for a potential impairment. In accordance with ASC 360-10, Accounting for the Impairment or Disposal of Long-Lived Assets , long-lived assets, such as property and equipment and intangible assets, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized by the amount by which the carrying amount of the asset exceeds the fair value of the asset. Cash and Cash Equivalents The Company considers cash invested in highly liquid financial instruments with maturities of three months or less at the date of purchase to be cash equivalents. Marketable Securities The Company generally holds securities until maturity; however, they may be sold under certain circumstances including, but not limited to, when necessary for the funding of acquisitions and other strategic investments. As a result the Company classifies its investment portfolio as available-for-sale. The Company classifies all investments with a maturity date greater than three months at the date of purchase as short-term marketable securities in its consolidated balance sheet. As of December 31, 2019 , and December 31, 2018 , the Company’s marketable securities consisted primarily of commercial paper, corporate bonds, government securities and/or other high-quality commercial securities. Employee Benefits Plan The Company sponsors a 401(k) tax-deferred savings plan for all employees in the United States who meet certain eligibility requirements. Participants may contribute up to the amount allowable as a deduction for federal income tax purposes. The Company is not required to contribute; however, the Company contributes a certain percentage of employee annual salaries on a discretionary basis, not to exceed an established threshold. The Company provided for a contribution of approximately $1.4 million , $1.3 million and $1.2 million in 2019 , 2018 and 2017 , respectively. Retirement Benefit Obligations (Pension) The Company recognizes the over-funded or under-funded status of a defined benefit pension or post-retirement plan as an asset or liability in the accompanying consolidated balance sheets. Actuarial gains and losses are recorded in accumulated other comprehensive loss, a component of stockholders’ equity, and are amortized as a component of net periodic cost over the remaining estimated service period of participants. Foreign Currency Risk and Foreign Currency Translation As of December 31, 2019 , the Company’s primary transactional currency was U.S. dollars; in addition, the Company holds cash in Swiss francs and euros to fund the operations of the Company’s Swiss subsidiary. The foreign exchange rate fluctuation between the U.S. dollar versus the Swiss franc and euro is recorded in other income in the consolidated statements of income. Gains and losses arising from the remeasurement of non-functional currency balances are recorded in other income in the accompanying consolidated statements of income. In the year ended December 31, 2019 , the Company realized a foreign exchange transaction loss of $0.3 million and a loss of $0.1 million in each of 2018 and 2017 . The functional currencies of the Company’s other subsidiaries are the local currencies. Accordingly, all assets and liabilities are translated into U.S. dollars at the current exchange rates as of the applicable balance sheet date. Revenues and expenses are translated at the average exchange rate prevailing during the period. Cumulative gains and losses from the translation of the foreign subsidiaries’ financial statements have been included in stockholders’ equity. Warranty The Company generally warrants that its products will substantially conform to the published specifications for 12 months from the date of shipment. The Company’s liability is limited to either a credit equal to the purchase price or replacement of the defective part. Returns under warranty have historically been immaterial, and as a result, the Company does not record a specific warranty reserve. Advertising Advertising costs are expensed as incurred. In 2019 , advertising costs amounted to $1.4 million and were $1.2 million and $1.3 million in each of 2018 and 2017 . Research and Development Research and development costs are expensed as incurred. Indemnifications The Company sells products to its distributors under contracts, collectively referred to as Distributor Sales Agreements (DSA). Each DSA contains the relevant terms of the contractual arrangement with the distributor, and generally includes certain provisions for indemnifying the distributor against losses, expenses, and liabilities from damages that may be awarded against the distributor in the event the Company’s products are found to infringe upon a patent, copyright, trademark, or other proprietary right of a third party (Customer Indemnification). The DSA generally limits the scope of and remedies for the Customer Indemnification obligations in a variety of industry-standard respects, including, but not limited to, limitations based on time and geography, and a right to replace an infringing product. The Company also, from time to time, has granted a specific indemnification right to individual customers. The Company believes its internal development processes and other policies and practices limit its exposure related to such indemnifications. In addition, the Company requires its employees to sign a proprietary information and inventions agreement, which assigns the rights to its employees' development work to the Company. To date, the Company has not had to reimburse any of its distributors or customers for any losses related to these indemnifications and no material claims were outstanding as of December 31, 2019 . For several reasons, including the lack of prior indemnification claims and the lack of a monetary liability limit for certain infringement cases, the Company cannot determine the maximum amount of potential future payments, if any, related to such indemnifications. Adoption of New Accounting Standards In February 2016, the FASB amended the existing accounting standards for leases, Accounting Standards Update (ASU) 2016-02 , Leases (Topic 842) . The amendments require lessees to recognize, on the balance sheet, assets and liabilities for the rights and obligations created by leases. The accounting by lessors will remain largely unchanged from that applied under previous U.S. GAAP. The Company adopted the new standards in the first quarter of 2019, effective January 1, 2019, using the optional transition method, under which the new standards were applied prospectively rather than restating the prior periods presented. The Company elected the practical expedients under the transition guidance, which includes the use of hindsight in determining the lease term and the practical expedient package to not reassess whether any expired or existing contracts are or contain leases, to not reassess the classification of any expired or existing leases, and to not reassess initial direct costs for any existing leases. In addition, the Company elected the practical expedient to recognize lease and non-lease components as a single lease component. The Company has elected not to record on the balance sheet leases with an initial term of twelve months or less. Upon adoption, the Company recognized both right-of-use assets and corresponding lease liabilities of approximately $7.3 million and $7.2 million , respectively, on the consolidated balance sheet. The difference between the right-of-use assets and lease liabilities was due to prepaid rent. There was no impact on the consolidated statement of income or the consolidated statement of cash flows. Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326) , which modifies the measurement of expected credit losses on certain financial instruments. In addition, for available-for-sale debt securities, the standard eliminates the concept of other-than-temporary impairment and requires the recognition of an allowance for credit losses rather than reductions in the amortized cost of the securities. The Company is required to adopt the new standards in the first quarter of fiscal 2020, with early adoption permitted. The amendments require a modified-retrospective approach with a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period. The Company does not expect the standard to have a material impact on its financial statements upon adoption.

COMPONENTS OF THE COMPANY'S CON

COMPONENTS OF THE COMPANY'S CONSOLIDATED BALANCE SHEETS	12 Months Ended
	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Supplemental Balance Sheet Disclosures [Text Block]	COMPONENTS OF THE COMPANY’S CONSOLIDATED BALANCE SHEETS: Accounts Receivable (in thousands) December 31, 2019 December 31, 2018 Accounts receivable trade $ 61,036 $ 54,055 Accrued ship and debit (33,475 ) (40,118 ) Allowance for stock rotation and rebate (2,524 ) (2,159 ) Allowance for doubtful accounts (763 ) (706 ) Total $ 24,274 $ 11,072 Inventories (in thousands) December 31, 2019 December 31, 2018 Raw materials $ 39,058 $ 41,138 Work-in-process 25,982 15,612 Finished goods 25,340 24,107 Total $ 90,380 $ 80,857 Prepaid Expenses and Other Current Assets (in thousands) December 31, 2019 December 31, 2018 Prepaid income tax $ 5,615 $ 3,081 Prepaid legal fees 16 181 Prepaid maintenance agreements 819 2,047 Advance to suppliers 3,579 2,157 Interest receivable 1,279 595 Other 4,289 3,854 Total $ 15,597 $ 11,915 Property and Equipment (in thousands) December 31, 2019 December 31, 2018 Land $ 21,790 $ 20,288 Construction-in-progress 18,604 21,696 Building and improvements 55,785 53,610 Machinery and equipment 168,576 160,028 Computer software and hardware and office furniture and fixtures 52,265 53,681 317,020 309,303 Accumulated depreciation (200,401 ) (195,186 ) Total $ 116,619 $ 114,117 Depreciation expense for property and equipment for fiscal years ended December 31, 2019 , 2018 and 2017 , was approximately $19.2 million , $18.9 million and $18.4 million , respectively, and was determined using the straight-line method over the following useful lives: Building and improvements 4-40 years Machinery and equipment 2-8 years Computer software and hardware and office furniture and fixtures 4-7 years Total property and equipment (excluding accumulated depreciation) located in the United States at December 31, 2019 , 2018 and 2017 , was approximately $160.7 million , $167.6 million and $159.5 million , respectively. In 2019 , approximately 14% of total property and equipment (excluding accumulated depreciation) was held in Thailand by one of the Company’s subcontractors. In each of 2018 and 2017 , 12% of total property and equipment was held in Thailand. No other country held 10% or more of total property and equipment in the periods presented. Accumulated Other Comprehensive Loss Changes in accumulated other comprehensive loss for the three years ended December 31, 2019 : (in thousands) Unrealized Gains and Losses on Available-for-Sale Securities Defined Benefit Pension Items Foreign Currency Items Total Balance at January 1, 2017 $ (220 ) $ (1,936 ) $ (554 ) $ (2,710 ) Other comprehensive income (loss) before reclassifications (207 ) 502 79 374 Amounts reclassified from accumulated other comprehensive loss — 197 (1) — 197 Other comprehensive income (207 ) 699 79 571 Balance at December 31, 2017 (427 ) (1,237 ) (475 ) (2,139 ) Other comprehensive income (loss) before reclassifications 161 401 (236 ) 326 Amounts reclassified from accumulated other comprehensive loss — 124 (1) — 124 Other comprehensive income 161 525 (236 ) 450 Balance at December 31, 2018 (266 ) (712 ) (711 ) (1,689 ) Other comprehensive income (loss) before reclassifications 849 (1,839 ) (518 ) (1,508 ) Amounts reclassified from accumulated other comprehensive loss — 67 (1) — 67 Other comprehensive loss 849 (1,772 ) (518 ) (1,441 ) Balance at December 31, 2019 $ 583 $ (2,484 ) $ (1,229 ) $ (3,130 ) _______________ (1) This component of accumulated other comprehensive loss is included in the computation of net periodic pension cost for the years ended December 31, 2019 , 2018 and 2017 .

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS [Text Block]	FAIR VALUE MEASUREMENTS: ASC 820-10, Fair Value Measurements , clarifies that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, ASC 820-10 establishes a three-tier value hierarchy, which prioritizes the inputs used in measuring fair value as follows: (Level 1) observable inputs such as quoted prices for identical assets in active markets; (Level 2) inputs other than the quoted prices in active markets that are observable either directly or indirectly; and (Level 3) unobservable inputs in which there is little or no market data, which requires the Company to develop its own assumptions. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. The Company’s cash equivalents and investment instruments are classified within Level 1 or Level 2 of the fair-value hierarchy because they are valued using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. The type of instrument valued based on quoted market prices in active markets primarily includes money market securities. This type of instrument is generally classified within Level 1 of the fair-value hierarchy. The types of instruments valued based on other observable inputs (Level 2 of the fair-value hierarchy) include investment-grade corporate bonds and commercial paper. Such types of investments are valued by using a multi-dimensional relational model, the inputs are primarily benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including market research publications. The Company does not hold any instruments that would be classified within Level 3 of the fair-value hierarchy. The fair value hierarchy of the Company’s cash equivalents and marketable securities at December 31, 2019 , and 2018 , was as follows: Fair Value Measurement at December 31, 2019 (in thousands) Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Corporate securities $ 232,398 $ — $ 232,398 Commercial paper 146,955 — 146,955 Money market funds 2,983 2,983 — Total $ 382,336 $ 2,983 $ 379,353 Fair Value Measurement at December 31, 2018 (in thousands) Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Corporate securities $ 94,451 $ — $ 94,451 Commercial paper 96,366 — 96,366 Money market funds 304 304 — Total $ 191,121 $ 304 $ 190,817 The Company did not transfer any investments between level 1 and level 2 of the fair value hierarchy in the years ended December 31, 2019 , and 2018 .

MARKETABLE SECURITIES

MARKETABLE SECURITIES	12 Months Ended
	Dec. 31, 2019
Marketable Securities [Abstract]
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]	MARKETABLE SECURITIES: Amortized cost and estimated fair market value of marketable securities classified as available-for-sale (excluding cash equivalents) at December 31, 2019 , were as follows: Amortized Gross Unrealized Estimated Fair (in thousands) Cost Gains Losses Market Value Investments due in 3 months or less: Corporate securities $ 15,934 $ 18 $ — $ 15,952 Total 15,934 18 — 15,952 Investments due in 4-12 months: Corporate securities 71,223 269 — 71,492 Total 71,223 269 — 71,492 Investments due in 12 months or greater: Corporate securities 144,658 302 (6 ) 144,954 Total 144,658 302 (6 ) 144,954 Total marketable securities $ 231,815 $ 589 $ (6 ) $ 232,398 Amortized cost and estimated fair market value of marketable securities classified as available-for-sale (excluding cash equivalents) at December 31, 2018 , were as follows: Amortized Gross Unrealized Estimated Fair (in thousands) Cost Gains Losses Market Value Investments due in 3 months or less: Corporate securities $ 6,788 $ — $ (2 ) $ 6,786 Total 6,788 — (2 ) 6,786 Investments due in 4-12 months: Corporate securities 60,123 — (244 ) 59,879 Total 60,123 — (244 ) 59,879 Investments due in 12 months or greater: Corporate securities 27,806 2 (22 ) 27,786 Total 27,806 2 (22 ) 27,786 Total marketable securities $ 94,717 $ 2 $ (268 ) $ 94,451 The weighted average interest rate of investments at December 31, 2019 and 2018 , was approximately 2.17% and 2.65% , respectively. As of December 31, 2019 and 2018 , there were no individual securities that had been in a continuous loss position for 12 months or greater.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS [Text Block]	GOODWILL AND INTANGIBLE ASSETS: The carrying amount of goodwill as of December 31, 2019 and 2018 was $91.8 million with no changes to goodwill in any of the respective fiscal years. Intangible assets consist primarily of developed technology, acquired licenses, customer relationships, trade name, domain name, in-process R&D and patent rights, and are reported net of accumulated amortization. The Company amortizes the cost of all intangible assets over the shorter of the estimated useful life or the term of the developed technology, customer relationships, technology licenses and in-place leases, which range from two to twelve years , with the exception of $1.3 million paid to acquire an internet domain name. The Company acquired the rights to the internet domain name www.power.com , which is now the Company’s primary domain name; the cost to acquire the domain name has been recorded as an intangible asset and will not be amortized as it has an indefinite useful life. Amortization of acquired intangible assets was approximately $5.2 million , $5.3 million and $6.1 million in the years ended December 31, 2019 , 2018 and 2017 , respectively. During the year ended December 31, 2019, the Company placed in service $4.7 million of in-process research and development intangible assets. The Company does not believe there is any significant residual value associated with the following intangible assets: December 31, 2019 December 31, 2018 (in thousands) Gross Accumulated Amortization Net Gross Accumulated Amortization Net Domain name $ 1,261 $ — $ 1,261 $ 1,261 $ — $ 1,261 In-process research and development — — — 4,690 — 4,690 Developed technology 37,960 (25,933 ) 12,027 33,270 (22,464 ) 10,806 Customer relationships 20,030 (18,098 ) 1,932 20,030 (16,520 ) 3,510 Technology licenses 1,926 (281 ) 1,645 1,000 (115 ) 885 Total intangible assets $ 61,177 $ (44,312 ) $ 16,865 $ 60,251 $ (39,099 ) $ 21,152 The estimated future amortization expense related to definite-lived intangible assets at December 31, 2019 , is as follows: Fiscal Year Estimated Amortization (in thousands) 2020 $ 4,359 2021 3,494 2022 2,415 2023 2,173 2024 1,279 Thereafter 1,884 Total $ 15,604

STOCK PLANS AND SHARE BASED COM

STOCK PLANS AND SHARE BASED COMPENSATION	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
STOCK PLANS AND SHARE BASED COMPENSATION [Text Block]	STOCK PLANS AND SHARE BASED COMPENSATION: Stock Plans As of December 31, 2019 , the Company had three stock-based compensation plans (the “Plans”) which are described below. 2007 Equity Incentive Plan The 2007 Equity Incentive Plan (2007 Plan) was adopted by the board of directors on September 10, 2007, and approved by the stockholders on November 7, 2007, as an amendment and restatement of the 1997 Stock Option Plan (1997 Plan). The 2007 Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock unit (RSU) awards, stock appreciation rights, performance-based (PSU) awards, long-term performance based (PRSU) awards and other stock awards to employees, directors and consultants. Pursuant to the 2007 Plan, the exercise price for incentive stock options and non-statutory stock options is generally at least 100% of the fair market value of the underlying shares on the date of grant. Options generally vest over 48 months measured from the date of grant. Options generally expire no later than ten years after the date of grant, subject to earlier termination upon an optionee’s cessation of employment or service. The 2007 Plan expired in September 2017 with no further grants to be made under this plan; however previous grants under this plan shall remain outstanding until they are exercised, vest, forfeited or expire. Beginning January 27, 2009, grants pursuant to the Directors Equity Compensation Program (which was adopted by the board of directors on January 27, 2009) to non-employee directors have been made primarily under the 2007 Plan. The Directors Equity Compensation Program provides for grants to outside directors as follows: effective annually, upon the first trading day of July, each outside director would receive a grant of an equity award with an aggregate value of $120,000 . At each outside director’s election, such award would consist entirely of RSUs or entirely of stock options. The quantity of options would be calculated by dividing $120,000 by the Black-Scholes value on the date of grant. The quantity of RSUs issued would be calculated by dividing $120,000 by the grant-date fair value. Further, on the date of election of a new outside director, such new director would receive such grant as continuing outside directors receive on the first trading day of July; provided, however, that such grant is prorated for the portion of the year that such new outside director will serve until the next first trading day of July. The Directors Equity Compensation Program will remain in effect at the discretion of the board of directors or the compensation committee. 2016 Incentive Award Plan The 2016 Incentive Award Plan (2016 Plan) was adopted by the board of directors on March 17, 2016 and approved by the stockholders on May 13, 2016. The Plan provides for the grant of RSU awards, PSU awards and PRSU awards. No other forms of equity-based awards, including stock options and stock appreciation rights, may be granted under the 2016 Plan. As of December 31, 2019 , 0.8 million awards have been issued and approximately 1.7 million shares of common stock remain available for future grant under the 2016 Plan. 1997 Employee Stock Purchase Plan Under the 1997 Employee Stock Purchase Plan (Purchase Plan), eligible employees may apply accumulated payroll deductions, which may not exceed 15% of an employee’s compensation, to the purchase of shares of the Company’s common stock at periodic intervals. The purchase price of stock under the Purchase Plan is equal to 85% of the lower of (i) the fair market value of the Company’s common stock on the first day of each offering period, or (ii) the fair market value of the Company’s common stock on the purchase date (as defined in the Purchase Plan). Each offering period consists of one purchase period of approximately six months duration. An aggregate of 3.5 million shares of common stock were reserved for issuance to employees under the Purchase Plan. As of December 31, 2019 , of the shares reserved for issuance, 3.2 million shares had been purchased and 0.3 million shares were reserved for future issuance under the Purchase Plan. Shares Reserved As of December 31, 2019 , the Company had approximately 2.1 million shares of common stock reserved for future grant under all stock plans. Stock-Based Compensation The Company applies the provisions of ASC 718-10, Stock Compensation . Under the provisions of ASC 718-10, the Company recognizes the fair value of stock-based compensation in its financial statements over the requisite service period of the individual grants, which generally equals a four -year vesting period. The Company uses estimates of volatility, expected term, risk-free interest rate, dividend yield and forfeitures in determining the fair value of these awards and the amount of compensation expense to recognize. The Company uses the straight-line method to amortize all stock awards granted over the requisite service period of the award. The following table summarizes the stock-based compensation expense recognized in accordance with ASC 718-10 for the years ended December 31, 2019 , 2018 and 2017 : Year Ended December 31, (in thousands) 2019 2018 2017 Cost of revenues $ 1,237 $ 1,097 $ 1,321 Research and development 8,423 7,688 8,496 Sales and marketing 5,015 4,729 5,197 General and administrative 8,672 8,066 9,663 Total stock-based compensation expense $ 23,347 $ 21,580 $ 24,677 The following table summarizes total compensation expense related to unvested awards not yet recognized, net of expected forfeitures, and the weighted average period over which it is expected to be recognized as of December 31, 2019 : Unrecognized Compensation Expense for Unvested Awards (in thousands) Weighted Average Remaining Recognition Period (in years) Long-term performance-based awards $ 1,693 2.00 Restricted stock units 35,276 2.94 Purchase plan 142 0.08 Total unrecognized compensation expense $ 37,111 Stock-based compensation expense in the year ended December 31, 2019 , was approximately $23.3 million (comprising approximately $17.5 million related to restricted stock units, $4.1 million related to performance-based awards and $1.7 million related to the Company’s Purchase Plan). Stock-based compensation expense in the year ended December 31, 2018 , was approximately $21.6 million (comprising approximately $16.6 million related to restricted stock units, $3.4 million related to performance-based awards and $1.6 million related to the Company’s Purchase Plan). Stock-based compensation expense in the year ended December 31, 2017 , was approximately $24.7 million (comprising approximately $15.2 million related to restricted stock units, $8.2 million related to performance-based awards and $1.3 million related to the Company’s Purchase Plan). The Company did not grant stock options in the years ended December 31, 2019 , 2018 and 2017 , and therefore no fair-value assumptions are reported. The fair value of employees’ stock purchase rights under the Purchase Plan was estimated using the Black-Scholes model with the following weighted-average assumptions used during the three years ended December 31, 2019 , 2018 and 2017 : Year Ended December 31, 2019 2018 2017 Risk-free interest rates 2.28% 1.94% 0.91% Expected volatility rates 37% 31% 30% Expected dividend yield 0.91% 0.89% 0.80% Expected term of purchase rights (in years) 0.50 0.50 0.50 Weighted-average estimated fair value of purchase rights $19.39 $17.33 $16.74 A summary of stock options outstanding as of December 31, 2019 , and activity during three years then ended, is presented below: (shares and intrinsic value in thousands) Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at January 1, 2017 697 $ 28.62 Granted — — Exercised (186 ) $ 27.48 Forfeited or expired — — Outstanding at December 31, 2017 511 $ 29.03 Granted — — Exercised (176 ) $ 22.60 Forfeited or expired — — Outstanding at December 31, 2018 335 $ 32.41 Granted — — Exercised (168 ) $ 25.96 Forfeited or expired — — Outstanding at December 31, 2019 167 $ 38.88 1.30 $ 10,051 Vested and Exercisable at December 31, 2019 167 1.30 $ 10,051 The total intrinsic value of options exercised during the year ended December 31, 2019 , 2018 and 2017 , was $8.3 million , $7.5 million and $8.9 million , respectively. The following table summarizes the stock options outstanding at December 31, 2019 : Options Outstanding Options Exercisable (shares in thousands) Range of Exercise Prices Options Outstanding Weighted Average Remaining Contractual Term (in years) Weighted Average Exercise Price Options Exercisable Weighted Average Exercise Price $32.26 - $38.07 92 0.74 $ 36.80 92 $ 36.80 $39.49 - $42.88 75 1.99 $ 41.43 75 $ 41.43 167 1.30 $ 38.88 167 $ 38.88 PSU Awards Under the performance-based awards program, the Company grants awards in the performance year in an amount equal to twice the target number of shares to be issued if the maximum performance metrics are met. The number of shares that are released at the end of the performance year can range from zero to 200% of the target number depending on the Company’s performance. The performance metrics of this program are annual targets consisting of a combination of net revenue, non-GAAP operating earnings and strategic goals. As the net revenue, non-GAAP operating income and strategic goals are considered performance conditions, expense associated with these awards, net of estimated forfeitures, is recognized over the service period based on an assessment of the achievement of the performance targets. The fair value of these PSUs is determined using the fair value of the Company’s common stock on the date of the grant, reduced by the discounted present value of dividends expected to be declared before the awards vest. If the performance conditions are not achieved, no compensation cost is recognized and any previously recognized compensation is reversed. A summary of PSU awards outstanding as of December 31, 2019 , and activity during the three years then ended, is presented below: (shares and intrinsic value in thousands) Shares Weighted Average Grant-Date Fair Value Per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at January 1, 2017 99 $ 46.25 Granted 88 $ 63.99 Vested (99 ) $ 46.25 Forfeited or canceled (9 ) $ 63.99 Outstanding at December 31, 2017 79 $ 63.99 Granted 89 $ 62.87 Vested (79 ) $ 63.99 Forfeited or canceled (63 ) $ 62.87 Outstanding at December 31, 2018 26 $ 62.87 Granted 93 $ 70.11 Vested (26 ) $ 62.87 Forfeited or canceled (32 ) $ 70.11 Outstanding at December 31, 2019 61 $ 70.11 — $ 5,999 Outstanding and expected to vest at December 31, 2019 61 — $ 5,999 The grant-date fair value of PSU awards released, which were fully vested, in the years ended December 31, 2019 , 2018 and 2017 were approximately $1.6 million , $5.1 million and $4.6 million , respectively. PRSU Awards (Long-term Performance Based) The Company's PRSU program provides for the issuance of PRSUs which will vest based on the Company's performance measured against the PRSU Plan's established revenue targets. The PRSUs were granted in an amount equal to twice the target number of shares to be issued if the maximum performance metrics are met. The actual number of shares the recipient receives is determined at the end of a three -year performance period based on results achieved versus the Company’s performance goals, and may range from zero to 200% of the target number. The performance goals for PRSUs granted in fiscal 2019 , 2018 and 2017 were based on the Company’s annual revenue growth over the respective three -year performance period. Recipients of a PRSU award generally must remain employed by the Company on a continuous basis through the end of the applicable three -year performance period in order to receive shares subject to that award. Expenses associated with these awards, net of estimated forfeitures, are recorded throughout the year depending on the number of shares expected to vest based on progress toward the performance target. The fair value of PRSU awards is determined using the fair value of the Company’s common stock on the grant date, reduced by the discounted present value of dividends expected to be declared before the awards vest. If the performance conditions are not achieved, no compensation cost is recognized and any previously recognized compensation is reversed. A summary of PRSU awards outstanding as of December 31, 2019 , and activity during the three years then ended, is presented below: (shares and intrinsic value in thousands) Shares Weighted Average Grant-Date Fair Value Per Share Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at January 1, 2017 150 $ 47.65 Granted 71 $ 63.00 Vested — — Forfeited or canceled (37 ) $ 51.59 Outstanding at December 31, 2017 184 $ 52.80 Granted 72 $ 59.90 Vested (38 ) $ 52.45 Forfeited or canceled (5 ) $ 43.26 Outstanding at December 31, 2018 213 $ 55.48 Granted 72 $ 68.17 Vested (70 ) $ 43.26 Forfeited or canceled (71 ) $ 63.00 Outstanding at December 31, 2019 144 $ 64.05 1.50 $ 14,203 Outstanding and expected to vest at December 31, 2019 58 2.00 $ 5,768 The grant-date fair value of PRSU awards released, which were fully vested, in the year ended December 31, 2019 and 2018 were approximately $3.0 million and $2.0 million , respectively. RSU Awards RSUs granted to employees typically vest ratably over a four -year period, and are converted into shares of the Company’s common stock upon vesting on a one-for-one basis subject to the employee’s continued service to the Company over that period. The fair value of RSUs is determined using the fair value of the Company’s common stock on the date of the grant, reduced by the discounted present value of dividends expected to be declared before the awards vest. Compensation expense is recognized on a straight-line basis over the requisite service period of each grant adjusted for estimated forfeitures. A summary of RSU awards outstanding as of December 31, 2019 , and activity during the three years then ended, is presented below: (shares and intrinsic value in thousands) Shares Weighted Average Grant-Date Fair Value Per Share Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at January 1, 2017 718 $ 47.54 Granted 558 $ 60.82 Vested (284 ) $ 46.52 Forfeited (44 ) $ 50.89 Outstanding at December 31, 2017 948 $ 55.51 Granted 275 $ 62.85 Vested (296 ) $ 53.78 Forfeited (32 ) $ 59.43 Outstanding at December 31, 2018 895 $ 58.19 Granted 291 $ 69.79 Vested (301 ) $ 56.19 Forfeited (25 ) $ 63.43 Outstanding at December 31, 2019 860 $ 62.66 1.58 $ 85,037 Outstanding and expected to vest at December 31, 2019 801 1.50 $ 79,192 The grant-date fair value of RSUs vested in the years ended December 31, 2019 , 2018 and 2017 , was approximately $16.9 million , $15.9 million and $13.2 million , respectively.

SIGNIFICANT CUSTOMERS AND GEOGR

SIGNIFICANT CUSTOMERS AND GEOGRAPHIC NET REVENUES	12 Months Ended
	Dec. 31, 2019
Risks and Uncertainties [Abstract]
SIGNIFICANT CUSTOMERS AND EXPORT SALES [Text Block]	SIGNIFICANT CUSTOMERS AND GEOGRAPHIC NET REVENUES: Customer Concentration The Company's top ten customers accounted for approximately 54% , 56% and 54% of revenues in 2019 , 2018 and 2017 , respectively. A significant portion of these revenues are attributable to sales of the Company’s products to distributors of electronic components. These distributors sell the Company’s products to a broad, diverse range of end users, including OEMs and merchant power supply manufacturers. Sales to distributors in 2019 , 2018 and 2017 were $304.6 million , $313.9 million and $330.9 million , respectively. Direct sales to OEMs and power-supply manufacturers accounted for the remainder. In each of 2019 , 2018 and 2017 one distributor accounted for more than 10% of revenues. The following table discloses this customer’s percentage of net revenues for the respective years: Year Ended December 31, Customer 2019 2018 2017 Avnet 11 % 14 % 16 % No other customers accounted for 10% or more of the Company’s net revenues in the periods presented. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consisted principally of cash investments and trade receivables. The Company does not have any off-balance-sheet credit exposure related to its customers. As of December 31, 2019 and December 31, 2018 , 63% and 64% of accounts receivable were concentrated with the Company’s top ten customers, respectively. The following customers represented 10% or more of accounts receivable: Customer December 31, December 31, Powertech Distribution Ltd. 10 % 11 % Avnet * 17 % _______________ * Total customer accounts receivable was less than 10% of net accounts receivables. No other customers accounted for 10% or more of the Company’s accounts receivable in the periods presented. Geographic Net Revenues The Company markets its products globally through its sales personnel and a worldwide network of independent sales representatives and distributors. Geographic net revenues based on “bill to” customer locations were as follows: Year Ended December 31, (In thousands) 2019 2018 2017 United States of America $ 10,662 $ 15,315 $ 16,647 Hong Kong/China 237,341 218,752 227,335 Taiwan 36,297 43,081 50,307 Korea 30,395 33,877 38,012 Western Europe (excluding Germany) 36,025 49,834 48,230 Japan 15,496 19,897 20,769 Germany 20,197 14,403 11,558 Other 34,256 20,796 18,897 Total net revenues $ 420,669 $ 415,955 $ 431,755

COMMON STOCK REPURCHASES AND CA

COMMON STOCK REPURCHASES AND CASH DIVIDENDS	12 Months Ended
	Dec. 31, 2019
Common Stock Repurchases and Cash Dividends [Abstract]
Stockholders' Equity [Text Block]	COMMON STOCK REPURCHASES AND CASH DIVIDENDS: Common Stock Repurchases Over the years the Company’s board of directors has authorized the use of funds to repurchase shares of the Company’s common stock, including $60.0 million , $30.0 million and $110.0 million in 2015, 2017, and 2018, respectively, with repurchases to be executed according to pre-defined price/volume guidelines. In 2017 , 2018 and 2019 the Company purchased approximately 129,000 , 1,572,000 and 121,000 shares, respectively, for approximately $9.2 million , $103.2 million and $7.3 million , respectively. As of December 31, 2019 , the Company had $43.9 million available for future stock repurchases, which has no expiration date. Authorization of future stock repurchase programs is at the discretion of the board of directors and will depend on the Company’s financial condition, results of operations, capital requirements and business conditions as well as other factors. Common Stock Dividend The following table presents the quarterly dividends declared per share of the Company’s common stock for the periods indicated: Year Ended December 31, 2019 2018 2017 First Quarter $ 0.17 $ 0.16 $ 0.14 Second Quarter $ 0.17 $ 0.16 $ 0.14 Third Quarter $ 0.17 $ 0.16 $ 0.14 Fourth Quarter $ 0.19 $ 0.16 $ 0.14 The Company paid a total of approximately $20.5 million , $18.8 million and $16.6 million in cash dividends during 2019 , 2018 and 2017 , respectively. In January 2019, the Company’s board of directors declared a $0.17 per share quarterly dividend for each quarter in 2019. In October 2019, the Company’s board of directors raised the cash dividends per share with the declaration of five cash dividends, consisting of (a) a dividend in the amount of $0.02 per share to be paid to stockholders of record at the end of the fourth quarter in 2019, which is in addition to the dividend in the amount of $0.17 per share to be paid to stockholders of record at the end of the fourth quarter in 2019 previously declared by the Board in January 2019, and (b) a dividend in the amount of $ 0.19 per share to be paid to stockholders of record at the end of each quarter in 2020. The declaration of any future cash dividend is at the discretion of the board of directors and will depend on the Company’s financial condition, results of operations, capital requirements, business conditions and other factors, as well as a determination that cash dividends are in the best interest of the Company’s stockholders.

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
EARNINGS PER SHARE [Text Block]	EARNINGS PER SHARE: Basic earnings per share are calculated by dividing net income by the weighted-average shares of common stock outstanding during the period. Diluted earnings per share are calculated by dividing net income by the weighted-average shares of common stock and dilutive common equivalent shares outstanding during the period. Dilutive common equivalent shares included in this calculation consist of dilutive shares issuable upon the assumed exercise of outstanding common stock options, the assumed vesting of outstanding restricted stock units, the assumed issuance of awards under the stock purchase plan and contingently issuable performance-based awards, as computed using the treasury stock method. A summary of the earnings per share calculation is as follows: Year Ended December 31, (in thousands, except per share amounts) 2019 2018 2017 Basic earnings per share: Net income $ 193,468 $ 69,984 $ 27,609 Weighted-average common shares 29,267 29,456 29,674 Basic earnings per share $ 6.61 $ 2.38 $ 0.93 Diluted earnings per share (1) : Net income $ 193,468 $ 69,984 $ 27,609 Weighted-average common shares 29,267 29,456 29,674 Effect of dilutive securities: Employee stock plans 549 691 871 Diluted weighted-average common shares 29,816 30,147 30,545 Diluted earnings per share $ 6.49 $ 2.32 $ 0.90 _______________ (1) The Company includes the shares underlying performance-based awards in the calculation of diluted earnings per share if the performance conditions have been satisfied as of the end of the reporting period and excludes such shares when the necessary conditions have not been met. The Company has included in the 2019, 2018 and 2017 calculations those shares that were contingently issuable upon the satisfaction of the performance conditions as of the end of the respective periods. In the years ended December 31, 2019 , 2018 , and 2017 , no outstanding stock awards were determined to be anti-dilutive and therefore were excluded from the computation of diluted earnings per share.

PROVISION FOR INCOME TAXES

PROVISION FOR INCOME TAXES	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
PROVISION FOR INCOME TAXES [Text Block]	PROVISION (BENEFIT) FOR INCOME TAXES: Income Taxes The Company accounts for income taxes under the provisions of ASC 740, Income Taxes . Under the provisions of ASC 740, deferred tax assets and liabilities are recognized based on the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, utilizing the tax rates that are expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. U.S. and foreign components of income before income taxes were: Year Ended December 31, (in thousands) 2019 2018 2017 U.S. operations $ 82,692 $ (6,529 ) $ (6,944 ) Foreign operations 139,722 66,293 67,243 Total income before income taxes $ 222,414 $ 59,764 $ 60,299 The components of the provision (benefit) for income taxes are as follows: Year Ended December 31, (in thousands) 2019 2018 2017 Current provision (benefit): Federal $ 18,293 $ (6,382 ) $ 35,311 State 184 4 4 Foreign 1,293 938 1,483 19,770 (5,440 ) 36,798 Deferred provision (benefit): Federal 9,683 (4,593 ) (3,640 ) State — — — Foreign (507 ) (187 ) (468 ) 9,176 (4,780 ) (4,108 ) Total $ 28,946 $ (10,220 ) $ 32,690 The provision (benefit) for income taxes differs from the amount that would result by applying the applicable federal income tax rate to income before income taxes, as follows: Year Ended December 31, 2019 2018 2017 Provision (benefit) computed at Federal statutory rate 21.0 % 21.0 % 35.0 % Business tax credits (2.4 ) (9.1 ) (5.7 ) Stock-based compensation (0.2 ) (2.2 ) (5.0 ) Foreign income taxed at different rate (12.7 ) (25.0 ) (37.3 ) GILTI inclusion 6.2 10.6 — U.S. Tax Act - transition tax 0.1 (16.2 ) 54.1 U.S. Tax Act - deferred tax asset and liability adjustment — — 8.1 Valuation allowance 0.8 2.8 2.2 Other 0.2 1.0 2.8 Total 13.0 % (17.1 )% 54.2 % The Company’s effective tax rate is impacted by the geographic distribution of the Company’s world-wide earnings in lower-tax jurisdictions, federal research tax credits and the recognition of excess tax benefits related to share-based payments. These benefits were partially offset by foreign income subject to U.S. tax, known as global intangible low-taxed income. The Company’s primary jurisdiction where foreign earnings are derived is the Cayman Islands, which is a non-taxing jurisdiction. Income earned in other foreign jurisdictions was not material. The Company has not been granted any incentivized tax rates and does not operate under any tax holidays in any jurisdiction. Additionally, in 2018 the Company’s effective tax rate was favorably impacted by revisions to the Tax Act resulting in a $9.7 million income tax benefit. In 2017 our effective tax rate was also impacted by a $37.5 million charge resulting from the enactment of the Tax Act. The components of the net deferred income tax assets (liabilities) were as follows: December 31, (in thousands) 2019 2018 Deferred tax assets: Other reserves and accruals $ 3,099 $ 3,695 Tax credit carry-forwards 18,968 18,052 Stock compensation 1,644 3,050 Capital losses 157 157 Net operating loss 899 3,144 Other 1,000 — Valuation allowance (20,822 ) (19,955 ) 4,945 8,143 Deferred tax liabilities: Depreciation (2,273 ) (1,423 ) Other — (30 ) (2,273 ) (1,453 ) Net deferred tax assets $ 2,672 $ 6,690 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 upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities and projected future taxable income. In the event that the Company determines, based on available evidence and management judgment, that all or part of the net deferred tax assets will not be realized in the future, the Company would record a valuation allowance in the period the determination is made. In addition, the calculation of tax liabilities involves significant judgment in estimating the impact of uncertainties in the application of complex tax laws. Resolution of these uncertainties in a manner inconsistent with the Company’s expectations could have a material impact on its results of operations and financial position. As of December 31, 2019 , the Company continues to maintain a valuation allowance primarily as a result of capital losses for federal purposes, and on its California, New Jersey and Canada deferred tax assets as the Company believes that it is not more likely than not that the deferred tax assets will be fully realized. As of December 31, 2019 , the Company had utilized all of its federal research and development tax credit carry-forwards. As of December 31, 2019 , the Company had California research and development tax credit carry-forwards of approximately $27.5 million (there is no expiration of research and development tax credit carry-forwards for the state of California) and California net operating losses of $24.6 million which will begin to expire in 2031. As of December 31, 2019 , the Company had Canadian scientific research and experimental development tax credit carry-forwards of approximately $3.1 million and New Jersey research and experimental development tax credit carry-forwards of approximately $0.7 million , which will start to expire in 2030 and 2026, respectively. The Tax Act signed into law on December 22, 2017, generally allows companies to repatriate accumulated foreign earnings without incurring additional U.S. federal taxes beginning after December 31, 2017. Accordingly, the Company has not provided for U.S. taxes on its undistributed earnings of foreign subsidiaries. The determination of the future tax consequences of the remittance of these earnings is not practicable. Unrecognized Tax Benefits The Company applies the provisions of ASC 740-10, relating to accounting for uncertain income taxes. Reconciliation of the beginning and ending amount of unrecognized tax benefits: (in thousands) Unrecognized Tax Benefits Unrecognized Tax Benefits Balance at January 1, 2017 $ 15,393 Gross Increase for Tax Positions of Current Year 1,699 Gross Decrease for Tax Positions of Prior Years (409 ) Unrecognized Tax Benefits Balance at December 31, 2017 16,683 Gross Increase for Tax Positions of Current Year 1,994 Gross Decrease for Tax Positions of Prior Years (70 ) Unrecognized Tax Benefits Balance at December 31, 2018 18,607 Gross Increase for Tax Positions of Current Year 1,379 Gross Decrease for Tax Positions of Prior Years (937 ) Unrecognized Tax Benefits Balance at December 31, 2019 $ 19,049 The Company's total unrecognized tax benefits as of December 31, 2019 , 2018 and 2017 , were $19.0 million , $18.6 million and $16.7 million , respectively. An income tax benefit of $10.6 million , net of valuation allowance adjustments, would be recorded if these unrecognized tax benefits are recognized. The Company cannot reasonably estimate the amount of the unrecognized tax benefit that could be adjusted in the next twelve months. The Company’s continuing practice is to recognize interest and/or penalties related to income tax matters in income tax expense. The Company had accrued interest and penalties of $0.1 million as of both December 31, 2019 and 2018, which have been recorded in long-term income taxes payable in the accompanying consolidated balance sheets. As of December 31, 2019 , the Company has concluded all U.S. federal income tax matters for the years through 2012. However, due to tax attributes, the IRS may calculate tax adjustments for subsequent years for positions taken prior to 2012. There are currently no pending income tax audits. On July 27, 2015, in Altera Corp. v. Commissioner, the U.S. Tax Court issued an opinion related to the treatment of stock-based compensation expense in an intercompany cost-sharing arrangement. A final decision was issued by the Tax Court in December 2015. In February 2016, the Commissioner appealed the Tax Court decision. On July 24, 2018, the U.S. Ninth Circuit Court of Appeals reversed the U.S. Tax Court’s decision Altera Corp. v. Commissioner; the reversal was subsequently withdrawn. On June 7, 2019, the Ninth Circuit Court of Appeals overturned the U.S. Tax Court decision. The Company has reviewed this case and its impact and concluded that no adjustment to the consolidated financial statements is appropriate at this time. The Company will continue to monitor ongoing developments and potential impacts to the consolidated financial statements.

LEASES AND COMMITMENTS

LEASES AND COMMITMENTS	12 Months Ended
	Dec. 31, 2019
Leases and Commitments [Abstract]
Leases and Commitments [Text Block]	LEASES AND COMMITEMENTS: Facilities and Leases The Company owns its main executive, administrative, manufacturing and technical offices in San Jose, California. The Company also owns a research and development facility in New Jersey and a test facility in Biel, Switzerland. The Company’s leases consist of operating leases for administrative office spaces, research-and-development facilities, design centers and sales offices in various countries around the world. The Company determines if an arrangement is a lease at inception. Some lease agreements contain lease and non-lease components, which are accounted for as a single lease component. Total lease expense was $2.5 million , $2.2 million and $2.0 million in the years ended December 31, 2019 , 2018 and 2017 , respectively, while short-term and variable lease expenses were not material during these periods. Balance sheet information related to leases was as follows: (In thousands) Balance Sheet Classification December 31, Right-of-use assets Operating lease assets Other assets $ 9,521 Lease liabilities Current operating lease liabilities Other accrued liabilities $ 1,954 Non-current operating lease liabilities Other liabilities 7,031 Total $ 8,985 Initial lease terms are determined at commencement and may include options to extend or terminate the lease when it is reasonably certain the Company will exercise the option. Remaining lease terms range from one to nine years , some of which include options to extend for up to six years , and some of which include options to terminate within one year . Leases with an initial term of twelve months or less are not recorded on the balance sheet. As the Company’s leases do not provide an implicit rate, the present value of future lease payments is determined using the Company’s incremental borrowing rate based on information available at commencement date. Lease term and discount rate December 31, Weighted average remaining lease term 4.8 years Weighted average discount rate 3.9 % Supplemental cash flows information related to leases was as follow: Year-ended (In thousands) December 31, Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 2,964 Right-of-use assets obtained in exchange for new operating lease obligations $ 4,884 Future minimum lease payments under all non-cancelable lease agreements as of December 31, 2019, are as follows: (In thousands) December 31, 2020 $ 2,131 2021 2,313 2022 1,923 2023 1,690 2024 699 Thereafter 1,082 Total future minimum lease payments 9,838 Less imputed interest (853 ) Total $ 8,985 Purchase Obligations At December 31, 2019 , the Company had no

LEGAL PROCEEDINGS AND CONTINGEN

LEGAL PROCEEDINGS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
LEGAL PROCEEDINGS AND CONTINGENCIES [Text Block]	LEGAL PROCEEDINGS AND CONTINGENCIES: From time to time in the ordinary course of business, the Company becomes involved in lawsuits, or customers and distributors may make claims against the Company. In accordance with ASC 450-10, Contingencies , the Company makes a provision for a liability when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. On October 4, 2019, the Company entered into a binding term sheet (the “Term Sheet”) with ON Semiconductor Corporation and its wholly owned subsidiaries Fairchild Semiconductor International, Inc., Fairchild Semiconductor Corporation, Fairchild (Taiwan) Corporation, and Semiconductor Components Industries, LLC (collectively, “ON”) pursuant to which the parties agreed to end all outstanding legal and administrative disputes. Pursuant to the Term Sheet, ON agreed to pay the Company $175.0 million in cash. In addition, each party agreed to release the other party from any claims to damages or monetary relief for certain alleged acts of patent infringement across the various patent infringement litigations, occurring on or before June 30, 2020, and not to file any additional action for legal or equitable relief prior to June 30, 2023 (although following that date a party may file a legal action for alleged patent infringement occurring after June 30, 2020). Neither party granted any licenses to the other. On October 19, 2019, the parties memorialized the terms of the Term Sheet in a definitive agreement (the “Definitive Agreement”). On October 22, 2019, the Company received ON’s payment of $175.0 million . Subject to the Definitive Agreement, the Company and ON have dismissed, withdrawn, and/or terminated all legal proceedings between the parties. The Company recorded a net $169.0 million favorable litigation settlement within operating expenses for the year ended December 31, 2019 in the consolidated statement of income. On April 1, 2016, Opticurrent, LLC filed a complaint against the Company in the United States District Court for the Eastern District of Texas. In its complaint, Opticurrent alleges that the Company has infringed and is infringing one patent pertaining to transistor switch devices. The Company filed a motion to transfer the case to California, which the Court granted, and the case was assigned to a new judge in San Francisco following the transfer. On December 21, 2018, the Court granted the Company’s challenge to Opticurrent’s damages expert but denied the Company’s motion for summary judgment. Following a trial in February 2019, a jury issued a finding of direct infringement by the Company but found that the Company did not induce infringement, and awarded Opticurrent damages of $6.7 million . The Company challenged those findings in post-trial proceedings, and the Court granted one of the Company’s post-trial motions, reducing the damages award to $1.2 million . The Company believes it has strong defenses, and intends to vigorously defend itself against Opticurrent’s claims through appeals, which are currently under way, with briefing completed and oral argument to follow in the coming months. On June 19, 2019, Opticurrent, LLC filed a follow-on lawsuit accusing more of the Company’s products of infringing the same claim of the same patent asserted in the parties’ prior litigation, as described above. The Company believes it has strong defenses, and intends to vigorously defend itself against Opticurrent’s claims, with appeals to follow if necessary. On January 6, 2020, the Company filed a complaint against CogniPower LLC for infringement of two of the Company’s patents and seeking a declaration of non-infringement with respect to three patents that CogniPower had charged the Company’s customers with infringing. The case is in its preliminary stages, and no schedule has been set for the case at this time, but the Company believes it has strong claims and defenses, and intends to vigorously defend itself against CogniPower’s infringement claims, with appeals to follow if necessary.

RETIREMENT PLANS

RETIREMENT PLANS	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
RETIREMENT PLANS [Text Block]	RETIREMENT PLANS: The Company sponsors a defined benefit pension plan (Pension Plan) for its Swiss subsidiary in accordance with the legal requirements of Switzerland. The plan assets, which provide benefits in the event of an employee’s retirement, death or disability, are held in legally autonomous trustee-administered funds that are subject to Swiss law. Benefits are based on the employee’s age, years of service and salary, and the plan is financed by contributions by both the employee and the Company. The net periodic benefit cost of the Pension Plan was not material to the Company's financial statements during the years ended December 31, 2019 , 2018 and 2017 . At December 31, 2019 , the projected benefit obligation was $14.8 million , the plan assets were $8.2 million and the net pension liability was $6.6 million . As of December 31, 2018 , the projected benefit obligation was $10.2 million , the plan assets were $6.4 million , and the net pension liability was $3.8 million . The Company has recorded the unfunded amount as a liability in its consolidated balance sheet at December 31, 2019 and 2018 , under the other liabilities caption. The Company expects to make contributions to the Pension Plan of approximately $0.4 million during 2020. The unrealized actuarial loss on pension benefits, net of tax, at December 31, 2019 , 2018 and 2017 was $2.5 million , $0.7 million and $1.2 million , respectively. These amounts were reflected in Note 3 under the caption accumulated other comprehensive loss. In accordance with the Compensation-Retirement Benefits Topic of ASC 715-20, Defined Benefits Plan

BANK LINE OF CREDIT

BANK LINE OF CREDIT	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
BANK LINE OF CREDIT [Text Block]	BANK LINE OF CREDIT: On July 27, 2016, the Company entered into a credit agreement with a bank (the "Credit Agreement") that provides the Company with a $75.0 million revolving line of credit to use for general corporate purposes with a $20.0 million sub-limit for the issuance of standby and trade letters of credit. The Credit Agreement was amended on April 30, 2018, to extend the termination date from July 26, 2019, to April 30, 2022, with all other terms remaining the same. The Company’s ability to borrow under the revolving line of credit is conditioned upon the Company’s compliance with specified covenants, including reporting and financial covenants, primarily a minimum cash requirement and a debt to earnings ratio. The Credit Agreement terminates on April 30, 2022; all advances under the revolving line of credit will become due on such date, or earlier in the event of a default. As of December 31, 2019 , $6.2 million was reserved against the available credit in the form a standby letter of credit. The Company was compliant with all covenants and had no advances outstanding under the Credit Agreement.

SELECTED QUARTERLY INFORMATION

SELECTED QUARTERLY INFORMATION	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
SELECTED QUARTERLY INFORMATION (Unaudited) [Text Block]	SELECTED QUARTERLY INFORMATION (Unaudited): The following tables set forth certain data from the Company's consolidated statements of income for each of the quarters in the years ended December 31, 2019 and 2018 . The unaudited quarterly consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements contained herein and include all adjustments that the Company considers necessary for a fair presentation of such information when read in conjunction with the Company’s annual audited consolidated financial statements and notes thereto appearing elsewhere in this report. The operating results for any quarter are not necessarily indicative of the results for any subsequent period or for the entire fiscal year. Three Months Ended (unaudited) Dec. 31, Sept. 30, June 30, Mar. 31, Dec. 31, Sept. 30, June 30, Mar. 31, (in thousands, except per share data) 2019 (1) 2019 2019 2019 2018 2018 2018 2018 Net revenues $ 114,457 $ 114,159 $ 102,865 $ 89,188 $ 93,307 $ 110,085 $ 109,482 $ 103,081 Gross profit 58,225 58,131 51,572 45,474 48,005 57,005 56,234 53,544 Net income $ 158,291 $ 17,099 $ 10,845 $ 7,233 $ 22,736 $ 17,667 $ 15,381 $ 14,200 Earnings per share Basic $ 5.38 $ 0.58 $ 0.37 $ 0.25 $ 0.78 $ 0.60 $ 0.52 $ 0.48 Diluted $ 5.28 $ 0.57 $ 0.37 $ 0.25 $ 0.77 $ 0.59 $ 0.51 $ 0.46 Shares used in per share calculation Basic 29,427 29,385 29,297 28,951 29,164 29,365 29,505 29,799 Diluted 30,005 29,866 29,702 29,446 29,651 29,998 30,183 30,552 _______________ (1) In October 2019 the Company entered into a favorable l itigation settlement with ON Semiconductor Corporation which resulted in a $169.0 million net gain (Refer to Note 13, Legal Proceedings and Contingencies , in our Notes to Consolidated Financial Statements included in this Annual Report on Form 10-K).

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts [Text Block]	Schedule II Valuation and Qualifying Accounts The Company maintains an allowance for the distributors’ ship and debit credits relating to the sell-through of the Company’s products. This reserve is established using the Company’s historical ship and debit amounts and levels of inventory in the distributor channels. The following is a summary of the activity in the allowance for ship and debit credits: (in thousands) Balance at Beginning of Period Charged to Costs and Expenses Deductions (1) Balance at End of Period Allowance for ship and debit credits: Year ended December 31, 2017 $ 38,075 $ 273,492 $ (272,081 ) $ 39,486 Year ended December 31, 2018 $ 39,486 $ 242,068 $ (241,436 ) $ 40,118 Year ended December 31, 2019 $ 40,118 $ 230,278 $ (236,921 ) $ 33,475 _______________ (1) Deductions relate to ship and debit credits issued which adjust the sales price from the standard distribution price to the pre-approved lower price. Refer to Note 2, Significant Accounting Policies and Recent Accounting Pronouncements , for the Company’s revenue recognition policy, including the Company’s accounting for ship and debit claims.

SIGNIFICANT ACCOUNTING POLICI_2

SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS Significant Accounting Policies and Estimates (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Segment Reporting [Policy Text Block]	Segment Reporting The Company is organized and operates as one reportable segment, the design, development, manufacture and marketing of integrated circuits and related components for use primarily in the high-voltage power conversion markets. The Company’s chief operating decision maker, the Chief Executive Officer, reviews financial information presented on a consolidated basis for purposes of making operating decisions and assessing financial performance.
Principles of Consolidation [Policy Text Block]	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries after elimination of all intercompany transactions and balances.
Estimates [Policy Text Block]	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 disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. On an ongoing basis, the Company evaluates its estimates, including those related to revenue recognition and allowances for receivables and inventories. These estimates are based on historical facts and various other factors, which the Company believes to be reasonable at the time the estimates are made. However, as the effects of future events cannot be determined with precision, actual results could differ significantly from management’s estimates.
Revenue Recognition [Policy Text Block]	Revenue Recognition The Company applies the provisions of Accounting Standards Codification (ASC) 606-10, Revenue from Contracts with Customers , and all related appropriate guidance. The Company recognizes revenue under the core principle to depict the transfer of control to the Company’s customers in an amount reflecting the consideration the Company expects to be entitled. In order to achieve that core principle, the Company applies the following five-step approach: (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when a performance obligation is satisfied. Product revenues consist of sales to original equipment manufacturers, or OEMs, merchant power supply manufacturers and distributors. The Company considers customer purchase orders, which in some cases are governed by master sales agreements, to be the contracts with a customer. In situations where sales are to a distributor, the Company has concluded that its contracts are with the distributor as the Company holds a contract bearing enforceable rights and obligations only with the distributor. As part of its consideration of the contract, the Company evaluates certain factors including the customer’s ability to pay (or credit risk). For each contract, the Company considers the promise to transfer products, each of which is distinct, to be the identified performance obligations. In determining the transaction price the Company evaluates whether the price is subject to refund or adjustment to determine the net consideration to which the Company expects to be entitled. As the Company’s standard payment terms are less than one year, the Company has elected the practical expedient under ASC 606-10-32-18 to not assess whether a contract has a significant financing component. The Company allocates the transaction price to each distinct product based on their relative standalone selling price. The product price as specified on the purchase order is considered the standalone selling price as it is an observable input which depicts the price as if sold to a similar customer in similar circumstances. Revenue is recognized when control of the product is transferred to the customer (i.e., when the Company’s performance obligation is satisfied), which typically occurs at shipment. Further, in determining whether control has transferred, the Company considers if there is a present right to payment and legal title, along with risks and rewards of ownership having transferred to the customer. Frequently, the Company receives orders for products to be delivered over multiple dates that may extend across several reporting periods. The Company invoices for each delivery upon shipment and recognizes revenues for each distinct product delivered, assuming transfer of control has occurred. As scheduled delivery dates are within one year, under the optional exemption provided by ASC 606-10-50-14 revenues allocated to future shipments of partially completed contracts are not disclosed. The Company has also elected the practical expedient under ASC 340-40-25-4 to expense commissions when incurred as the amortization period of the commission asset the Company would have otherwise recognized is less than one year. Sales to international customers that are shipped from the Company’s facility outside of the United States are pursuant to EX Works, or EXW, shipping terms, meaning that control of the product transfers to the customer upon shipment from the Company’s foreign warehouse. Sales to international customers that are shipped from the Company’s facility in California are pursuant to Delivered at Frontier, or DAF, shipping terms. As such, control of the product passes to the customer when the shipment reaches the destination country and revenue is recognized upon the arrival of the product in that country. Shipments to customers in the Americas are pursuant to Free on Board, or FOB, point of origin shipping terms meaning that control is passed to the customer upon shipment. Sales to most distributors are made under terms allowing certain price adjustments and limited rights of return (known as “stock rotation”) of the Company’s products held in their inventory or upon sale to their end customers. Revenue from sales to distributors is recognized upon the transfer of control to the distributor. Frequently, distributors need to sell at a price lower than the standard distribution price in order to win business. At the time the distributor invoices its customer or soon thereafter, the distributor submits a “ship and debit” price adjustment claim to the Company to adjust the distributor’s cost from the standard price to the pre-approved lower price. After the Company verifies that the claim was pre-approved, a credit memo is issued to the distributor for the ship and debit claim. In determining the transaction price, the Company considers ship and debit price adjustments to be variable consideration. Such price adjustments are estimated using the expected value method based on an analysis of actual ship and debit claims, at the distributor and product level, over a period of time considered adequate to account for current pricing and business trends. Historically, actual price adjustments for ship and debit claims relative to those estimated and included when determining the transaction price have not materially differed. Stock rotation rights grant the distributor the ability to return certain specified amounts of inventory. Stock rotation adjustments are an additional form of variable consideration and are also estimated using the expected value method based on historical return rates. Historically, distributor stock rotation adjustments have not been material. Sales to certain distributors are made under terms that do not include rights of return or price concessions after the product is shipped to the distributor. Accordingly, upon application of steps one through five above, product revenue is recognized upon shipment and transfer of control. The Company generally provides an assurance warranty that its products will substantially conform to the published specifications for twelve months from the date of shipment. The Company’s liability is limited to either a credit equal to the purchase price or replacement of the defective part. Returns under warranty have historically been immaterial. As such, the Company does not record a specific warranty reserve or consider activities related to such warranty, if any, to be a separate performance obligation.
Inventories [Policy Text Block]	Inventories Inventories (which consist of costs associated with the purchases of wafers from domestic and offshore foundries and of packaged components from offshore assembly manufacturers, as well as internal labor and overhead associated with the testing of both wafers and packaged components) are stated at the lower of cost (first-in, first-out) or market. Provisions, when required, are made to reduce excess and obsolete inventories to their estimated net realizable values.
Income Taxes [Policy Text Block]	Income Taxes Income-tax expense is an estimate of current income taxes payable or refundable in the current fiscal year based on reported income before income taxes. Deferred income taxes reflect the effect of temporary differences and carry-forwards that are recognized for financial reporting and income tax purposes. The Company accounts for income taxes under the provisions of ASC 740, Income Taxe s. Under the provisions of ASC 740, deferred tax assets and liabilities are recognized based on the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, utilizing the tax rates that are expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company recognizes valuation allowances to reduce any deferred tax assets to the amount that it estimates will more likely than not be realized based on available evidence and management’s judgment. The Company limits the deferred tax assets recognized related to certain officers’ compensation to amounts that it estimates will be deductible in future periods based upon Internal Revenue Code Section 162(m). In the event that the Company determines, based on available evidence and management judgment, that all or part of the net deferred tax assets will not be realized in the future, it would record a valuation allowance in the period the determination is made. In addition, the calculation of tax liabilities involves significant judgment in estimating the impact of uncertainties in the application of complex tax laws. Resolution of these uncertainties in a manner inconsistent with the Company’s expectations could have a material impact on the Company’s results of operations and financial position.
Business Combinations [Policy Text Block]	Business Combinations The purchase price of an acquisition is allocated to the underlying assets acquired and liabilities assumed based upon their estimated fair values at the date of acquisition. To the extent the purchase price exceeds the fair value of the net identifiable tangible and intangible assets acquired and liabilities assumed, such excess is allocated to goodwill. The Company determines the estimated fair values after review and consideration of relevant information, including discounted cash flows, quoted market prices and estimates made by management. The Company adjusts the preliminary purchase price allocation, as necessary, during the measurement period of up to one year after the acquisition closing date as it obtains more information as to facts and circumstances existing at the acquisition date impacting asset valuations and liabilities assumed. Acquisition-related costs are recognized separately from the acquisition and are expensed as incurred.
Goodwill and Intangible Assets [Policy Text Block]	Goodwill and Intangible Assets Goodwill and the Company's domain name are evaluated in accordance with ASC 350-10, Goodwill and Other Intangible Assets, and an impairment analysis is conducted on an annual basis, or sooner if indicators exist for a potential impairment. In accordance with ASC 360-10, Accounting for the Impairment or Disposal of Long-Lived Assets , long-lived assets, such as property and equipment and intangible assets, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized by the amount by which the carrying amount of the asset exceeds the fair value of the asset.
Cash and Cash Equivalents [Policy Text Block]	Cash and Cash Equivalents
Marketable Securities [Policy Text Block]	Marketable Securities The Company generally holds securities until maturity; however, they may be sold under certain circumstances including, but not limited to, when necessary for the funding of acquisitions and other strategic investments. As a result the Company classifies its investment portfolio as available-for-sale. The Company classifies all investments with a maturity date greater than three months at the date of purchase as short-term marketable securities in its consolidated balance sheet. As of December 31, 2019 , and December 31, 2018 , the Company’s marketable securities consisted primarily of commercial paper, corporate bonds, government securities and/or other high-quality commercial securities.
Employee Benefits Plan [Policy Text Block]	Employee Benefits Plan The Company sponsors a 401(k) tax-deferred savings plan for all employees in the United States who meet certain eligibility requirements. Participants may contribute up to the amount allowable as a deduction for federal income tax purposes. The Company is not required to contribute; however, the Company contributes a certain percentage of employee annual salaries on a discretionary basis, not to exceed an established threshold. The Company provided for a contribution of approximately $1.4 million , $1.3 million and $1.2 million in 2019 , 2018 and 2017 , respectively.
Retirement Benefit Obligations (Pension) [Policy Text Block]	Retirement Benefit Obligations (Pension) The Company recognizes the over-funded or under-funded status of a defined benefit pension or post-retirement plan as an asset or liability in the accompanying consolidated balance sheets. Actuarial gains and losses are recorded in accumulated other comprehensive loss, a component of stockholders’ equity, and are amortized as a component of net periodic cost over the remaining estimated service period of participants.
Foreign Currency Risk and Foreign Currency Translations [Policy Text Block]	Foreign Currency Risk and Foreign Currency Translation As of December 31, 2019 , the Company’s primary transactional currency was U.S. dollars; in addition, the Company holds cash in Swiss francs and euros to fund the operations of the Company’s Swiss subsidiary. The foreign exchange rate fluctuation between the U.S. dollar versus the Swiss franc and euro is recorded in other income in the consolidated statements of income. Gains and losses arising from the remeasurement of non-functional currency balances are recorded in other income in the accompanying consolidated statements of income. In the year ended December 31, 2019 , the Company realized a foreign exchange transaction loss of $0.3 million and a loss of $0.1 million in each of 2018 and 2017 . The functional currencies of the Company’s other subsidiaries are the local currencies. Accordingly, all assets and liabilities are translated into U.S. dollars at the current exchange rates as of the applicable balance sheet date. Revenues and expenses are translated at the average exchange rate prevailing during the period. Cumulative gains and losses from the translation of the foreign subsidiaries’ financial statements have been included in stockholders’ equity.
Warranty [Policy Text Block]	Warranty The Company generally warrants that its products will substantially conform to the published specifications for 12 months from the date of shipment. The Company’s liability is limited to either a credit equal to the purchase price or replacement of the defective part. Returns under warranty have historically been immaterial, and as a result, the Company does not record a specific warranty reserve.
Advertising [Policy Text Block]	Advertising Advertising costs are expensed as incurred. In 2019 , advertising costs amounted to $1.4 million and were $1.2 million and $1.3 million in each of 2018 and 2017 .
Research and Development [Policy Text Block]	Research and Development Research and development costs are expensed as incurred.
Indemnifications [Policy Text Block]	Indemnifications The Company sells products to its distributors under contracts, collectively referred to as Distributor Sales Agreements (DSA). Each DSA contains the relevant terms of the contractual arrangement with the distributor, and generally includes certain provisions for indemnifying the distributor against losses, expenses, and liabilities from damages that may be awarded against the distributor in the event the Company’s products are found to infringe upon a patent, copyright, trademark, or other proprietary right of a third party (Customer Indemnification). The DSA generally limits the scope of and remedies for the Customer Indemnification obligations in a variety of industry-standard respects, including, but not limited to, limitations based on time and geography, and a right to replace an infringing product. The Company also, from time to time, has granted a specific indemnification right to individual customers. The Company believes its internal development processes and other policies and practices limit its exposure related to such indemnifications. In addition, the Company requires its employees to sign a proprietary information and inventions agreement, which assigns the rights to its employees' development work to the Company. To date, the Company has not had to reimburse any of its distributors or customers for any losses related to these indemnifications and no material claims were outstanding as of December 31, 2019 . For several reasons, including the lack of prior indemnification claims and the lack of a monetary liability limit for certain infringement cases, the Company cannot determine the maximum amount of potential future payments, if any, related to such indemnifications.
Fair Value of Financial Instruments, Policy [Policy Text Block]	The Company’s cash equivalents and investment instruments are classified within Level 1 or Level 2 of the fair-value hierarchy because they are valued using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. The type of instrument valued based on quoted market prices in active markets primarily includes money market securities. This type of instrument is generally classified within Level 1 of the fair-value hierarchy. The types of instruments valued based on other observable inputs (Level 2 of the fair-value hierarchy) include investment-grade corporate bonds and commercial paper. Such types of investments are valued by using a multi-dimensional relational model, the inputs are primarily benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including market research publications.
Share-based Compensation [Policy Text Block]	Stock-Based Compensation The Company applies the provisions of ASC 718-10, Stock Compensation . Under the provisions of ASC 718-10, the Company recognizes the fair value of stock-based compensation in its financial statements over the requisite service period of the individual grants, which generally equals a four -year vesting period. The Company uses estimates of volatility, expected term, risk-free interest rate, dividend yield and forfeitures in determining the fair value of these awards and the amount of compensation expense to recognize. The Company uses the straight-line method to amortize all stock awards granted over the requisite service period of the award.

COMPONENTS OF THE COMPANY'S C_2

COMPONENTS OF THE COMPANY'S CONSOLIDATED BALANCE SHEETS (Tables)	12 Months Ended
	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Schedule of Accounts Receivable [Table Text Block]	Accounts Receivable (in thousands) December 31, 2019 December 31, 2018 Accounts receivable trade $ 61,036 $ 54,055 Accrued ship and debit (33,475 ) (40,118 ) Allowance for stock rotation and rebate (2,524 ) (2,159 ) Allowance for doubtful accounts (763 ) (706 ) Total $ 24,274 $ 11,072
Schedule of Inventory, Current [Table Text Block]	Inventories (in thousands) December 31, 2019 December 31, 2018 Raw materials $ 39,058 $ 41,138 Work-in-process 25,982 15,612 Finished goods 25,340 24,107 Total $ 90,380 $ 80,857
Schedule of Prepaid Expenses and Other Current Assets [Table Text Block]	Prepaid Expenses and Other Current Assets (in thousands) December 31, 2019 December 31, 2018 Prepaid income tax $ 5,615 $ 3,081 Prepaid legal fees 16 181 Prepaid maintenance agreements 819 2,047 Advance to suppliers 3,579 2,157 Interest receivable 1,279 595 Other 4,289 3,854 Total $ 15,597 $ 11,915
Property and Equipment [Table Text Block]	Property and Equipment (in thousands) December 31, 2019 December 31, 2018 Land $ 21,790 $ 20,288 Construction-in-progress 18,604 21,696 Building and improvements 55,785 53,610 Machinery and equipment 168,576 160,028 Computer software and hardware and office furniture and fixtures 52,265 53,681 317,020 309,303 Accumulated depreciation (200,401 ) (195,186 ) Total $ 116,619 $ 114,117
Property and Equipment Useful Lives [Table Text Block]	Building and improvements 4-40 years Machinery and equipment 2-8 years Computer software and hardware and office furniture and fixtures 4-7 years
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Changes in accumulated other comprehensive loss for the three years ended December 31, 2019 : (in thousands) Unrealized Gains and Losses on Available-for-Sale Securities Defined Benefit Pension Items Foreign Currency Items Total Balance at January 1, 2017 $ (220 ) $ (1,936 ) $ (554 ) $ (2,710 ) Other comprehensive income (loss) before reclassifications (207 ) 502 79 374 Amounts reclassified from accumulated other comprehensive loss — 197 (1) — 197 Other comprehensive income (207 ) 699 79 571 Balance at December 31, 2017 (427 ) (1,237 ) (475 ) (2,139 ) Other comprehensive income (loss) before reclassifications 161 401 (236 ) 326 Amounts reclassified from accumulated other comprehensive loss — 124 (1) — 124 Other comprehensive income 161 525 (236 ) 450 Balance at December 31, 2018 (266 ) (712 ) (711 ) (1,689 ) Other comprehensive income (loss) before reclassifications 849 (1,839 ) (518 ) (1,508 ) Amounts reclassified from accumulated other comprehensive loss — 67 (1) — 67 Other comprehensive loss 849 (1,772 ) (518 ) (1,441 ) Balance at December 31, 2019 $ 583 $ (2,484 ) $ (1,229 ) $ (3,130 ) _______________ (1) This component of accumulated other comprehensive loss is included in the computation of net periodic pension cost for the years ended December 31, 2019 , 2018 and 2017 .

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Of Marketable Securities and Investments [Table Text Block]	The fair value hierarchy of the Company’s cash equivalents and marketable securities at December 31, 2019 , and 2018 , was as follows: Fair Value Measurement at December 31, 2019 (in thousands) Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Corporate securities $ 232,398 $ — $ 232,398 Commercial paper 146,955 — 146,955 Money market funds 2,983 2,983 — Total $ 382,336 $ 2,983 $ 379,353 Fair Value Measurement at December 31, 2018 (in thousands) Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Corporate securities $ 94,451 $ — $ 94,451 Commercial paper 96,366 — 96,366 Money market funds 304 304 — Total $ 191,121 $ 304 $ 190,817

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	12 Months Ended
	Dec. 31, 2019
Marketable Securities [Abstract]
Available-for-sale Securities [Table Text Block]	Amortized cost and estimated fair market value of marketable securities classified as available-for-sale (excluding cash equivalents) at December 31, 2019 , were as follows: Amortized Gross Unrealized Estimated Fair (in thousands) Cost Gains Losses Market Value Investments due in 3 months or less: Corporate securities $ 15,934 $ 18 $ — $ 15,952 Total 15,934 18 — 15,952 Investments due in 4-12 months: Corporate securities 71,223 269 — 71,492 Total 71,223 269 — 71,492 Investments due in 12 months or greater: Corporate securities 144,658 302 (6 ) 144,954 Total 144,658 302 (6 ) 144,954 Total marketable securities $ 231,815 $ 589 $ (6 ) $ 232,398 Amortized cost and estimated fair market value of marketable securities classified as available-for-sale (excluding cash equivalents) at December 31, 2018 , were as follows: Amortized Gross Unrealized Estimated Fair (in thousands) Cost Gains Losses Market Value Investments due in 3 months or less: Corporate securities $ 6,788 $ — $ (2 ) $ 6,786 Total 6,788 — (2 ) 6,786 Investments due in 4-12 months: Corporate securities 60,123 — (244 ) 59,879 Total 60,123 — (244 ) 59,879 Investments due in 12 months or greater: Corporate securities 27,806 2 (22 ) 27,786 Total 27,806 2 (22 ) 27,786 Total marketable securities $ 94,717 $ 2 $ (268 ) $ 94,451

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of intangible assets [Table Text Block]	The Company does not believe there is any significant residual value associated with the following intangible assets: December 31, 2019 December 31, 2018 (in thousands) Gross Accumulated Amortization Net Gross Accumulated Amortization Net Domain name $ 1,261 $ — $ 1,261 $ 1,261 $ — $ 1,261 In-process research and development — — — 4,690 — 4,690 Developed technology 37,960 (25,933 ) 12,027 33,270 (22,464 ) 10,806 Customer relationships 20,030 (18,098 ) 1,932 20,030 (16,520 ) 3,510 Technology licenses 1,926 (281 ) 1,645 1,000 (115 ) 885 Total intangible assets $ 61,177 $ (44,312 ) $ 16,865 $ 60,251 $ (39,099 ) $ 21,152
Schedule of expected amortization expense [Table Text Block]	The estimated future amortization expense related to definite-lived intangible assets at December 31, 2019 , is as follows: Fiscal Year Estimated Amortization (in thousands) 2020 $ 4,359 2021 3,494 2022 2,415 2023 2,173 2024 1,279 Thereafter 1,884 Total $ 15,604

STOCK PLANS AND SHARE BASED C_2

STOCK PLANS AND SHARE BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of stock-based compensation expense [Table Text Block]	The following table summarizes the stock-based compensation expense recognized in accordance with ASC 718-10 for the years ended December 31, 2019 , 2018 and 2017 : Year Ended December 31, (in thousands) 2019 2018 2017 Cost of revenues $ 1,237 $ 1,097 $ 1,321 Research and development 8,423 7,688 8,496 Sales and marketing 5,015 4,729 5,197 General and administrative 8,672 8,066 9,663 Total stock-based compensation expense $ 23,347 $ 21,580 $ 24,677
Share-based Payment Arrangement, Nonvested Award, Cost [Table Text Block]	The following table summarizes total compensation expense related to unvested awards not yet recognized, net of expected forfeitures, and the weighted average period over which it is expected to be recognized as of December 31, 2019 : Unrecognized Compensation Expense for Unvested Awards (in thousands) Weighted Average Remaining Recognition Period (in years) Long-term performance-based awards $ 1,693 2.00 Restricted stock units 35,276 2.94 Purchase plan 142 0.08 Total unrecognized compensation expense $ 37,111
Fair value assumptions for employees' stock purchase rights under the Purchase Plan [Table Text Block]	The fair value of employees’ stock purchase rights under the Purchase Plan was estimated using the Black-Scholes model with the following weighted-average assumptions used during the three years ended December 31, 2019 , 2018 and 2017 : Year Ended December 31, 2019 2018 2017 Risk-free interest rates 2.28% 1.94% 0.91% Expected volatility rates 37% 31% 30% Expected dividend yield 0.91% 0.89% 0.80% Expected term of purchase rights (in years) 0.50 0.50 0.50 Weighted-average estimated fair value of purchase rights $19.39 $17.33 $16.74
Summary of option activity under the Plans [Table Text Block]	A summary of stock options outstanding as of December 31, 2019 , and activity during three years then ended, is presented below: (shares and intrinsic value in thousands) Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at January 1, 2017 697 $ 28.62 Granted — — Exercised (186 ) $ 27.48 Forfeited or expired — — Outstanding at December 31, 2017 511 $ 29.03 Granted — — Exercised (176 ) $ 22.60 Forfeited or expired — — Outstanding at December 31, 2018 335 $ 32.41 Granted — — Exercised (168 ) $ 25.96 Forfeited or expired — — Outstanding at December 31, 2019 167 $ 38.88 1.30 $ 10,051 Vested and Exercisable at December 31, 2019 167 1.30 $ 10,051
Summary of stock options outstanding by exercise price range [Table Text Block]	The following table summarizes the stock options outstanding at December 31, 2019 : Options Outstanding Options Exercisable (shares in thousands) Range of Exercise Prices Options Outstanding Weighted Average Remaining Contractual Term (in years) Weighted Average Exercise Price Options Exercisable Weighted Average Exercise Price $32.26 - $38.07 92 0.74 $ 36.80 92 $ 36.80 $39.49 - $42.88 75 1.99 $ 41.43 75 $ 41.43 167 1.30 $ 38.88 167 $ 38.88
Summary of restricted stock units outstanding [Table Text Block]	A summary of RSU awards outstanding as of December 31, 2019 , and activity during the three years then ended, is presented below: (shares and intrinsic value in thousands) Shares Weighted Average Grant-Date Fair Value Per Share Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at January 1, 2017 718 $ 47.54 Granted 558 $ 60.82 Vested (284 ) $ 46.52 Forfeited (44 ) $ 50.89 Outstanding at December 31, 2017 948 $ 55.51 Granted 275 $ 62.85 Vested (296 ) $ 53.78 Forfeited (32 ) $ 59.43 Outstanding at December 31, 2018 895 $ 58.19 Granted 291 $ 69.79 Vested (301 ) $ 56.19 Forfeited (25 ) $ 63.43 Outstanding at December 31, 2019 860 $ 62.66 1.58 $ 85,037 Outstanding and expected to vest at December 31, 2019 801 1.50 $ 79,192
Performance Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of performance-based awards outstanding [Table Text Block]	A summary of PSU awards outstanding as of December 31, 2019 , and activity during the three years then ended, is presented below: (shares and intrinsic value in thousands) Shares Weighted Average Grant-Date Fair Value Per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at January 1, 2017 99 $ 46.25 Granted 88 $ 63.99 Vested (99 ) $ 46.25 Forfeited or canceled (9 ) $ 63.99 Outstanding at December 31, 2017 79 $ 63.99 Granted 89 $ 62.87 Vested (79 ) $ 63.99 Forfeited or canceled (63 ) $ 62.87 Outstanding at December 31, 2018 26 $ 62.87 Granted 93 $ 70.11 Vested (26 ) $ 62.87 Forfeited or canceled (32 ) $ 70.11 Outstanding at December 31, 2019 61 $ 70.11 — $ 5,999 Outstanding and expected to vest at December 31, 2019 61 — $ 5,999
Long-Term Performance-based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of performance-based awards outstanding [Table Text Block]	A summary of PRSU awards outstanding as of December 31, 2019 , and activity during the three years then ended, is presented below: (shares and intrinsic value in thousands) Shares Weighted Average Grant-Date Fair Value Per Share Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at January 1, 2017 150 $ 47.65 Granted 71 $ 63.00 Vested — — Forfeited or canceled (37 ) $ 51.59 Outstanding at December 31, 2017 184 $ 52.80 Granted 72 $ 59.90 Vested (38 ) $ 52.45 Forfeited or canceled (5 ) $ 43.26 Outstanding at December 31, 2018 213 $ 55.48 Granted 72 $ 68.17 Vested (70 ) $ 43.26 Forfeited or canceled (71 ) $ 63.00 Outstanding at December 31, 2019 144 $ 64.05 1.50 $ 14,203 Outstanding and expected to vest at December 31, 2019 58 2.00 $ 5,768

SIGNIFICANT CUSTOMERS AND GEO_2

SIGNIFICANT CUSTOMERS AND GEOGRAPHIC NET REVENUES (Tables)	12 Months Ended
	Dec. 31, 2019
Risks and Uncertainties [Abstract]
Customers accounted for 10% or more of total net revenues [Table Text Block]	The following table discloses this customer’s percentage of net revenues for the respective years: Year Ended December 31, Customer 2019 2018 2017 Avnet 11 % 14 % 16 %
Customers representing 10% or more of accounts receivable [Table Text Block]	The following customers represented 10% or more of accounts receivable: Customer December 31, December 31, Powertech Distribution Ltd. 10 % 11 % Avnet * 17 % _______________ * Total customer accounts receivable was less than 10% of net accounts receivables.
Geographic net revenues	Geographic net revenues based on “bill to” customer locations were as follows: Year Ended December 31, (In thousands) 2019 2018 2017 United States of America $ 10,662 $ 15,315 $ 16,647 Hong Kong/China 237,341 218,752 227,335 Taiwan 36,297 43,081 50,307 Korea 30,395 33,877 38,012 Western Europe (excluding Germany) 36,025 49,834 48,230 Japan 15,496 19,897 20,769 Germany 20,197 14,403 11,558 Other 34,256 20,796 18,897 Total net revenues $ 420,669 $ 415,955 $ 431,755

COMMON STOCK REPURCHASES AND _2

COMMON STOCK REPURCHASES AND CASH DIVIDENDS (Tables)	12 Months Ended
	Dec. 31, 2019
Common Stock Repurchases and Cash Dividends [Abstract]
Dividends Declared [Table Text Block]	The following table presents the quarterly dividends declared per share of the Company’s common stock for the periods indicated: Year Ended December 31, 2019 2018 2017 First Quarter $ 0.17 $ 0.16 $ 0.14 Second Quarter $ 0.17 $ 0.16 $ 0.14 Third Quarter $ 0.17 $ 0.16 $ 0.14 Fourth Quarter $ 0.19 $ 0.16 $ 0.14

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings per share calculation [Table Text Block]	A summary of the earnings per share calculation is as follows: Year Ended December 31, (in thousands, except per share amounts) 2019 2018 2017 Basic earnings per share: Net income $ 193,468 $ 69,984 $ 27,609 Weighted-average common shares 29,267 29,456 29,674 Basic earnings per share $ 6.61 $ 2.38 $ 0.93 Diluted earnings per share (1) : Net income $ 193,468 $ 69,984 $ 27,609 Weighted-average common shares 29,267 29,456 29,674 Effect of dilutive securities: Employee stock plans 549 691 871 Diluted weighted-average common shares 29,816 30,147 30,545 Diluted earnings per share $ 6.49 $ 2.32 $ 0.90 _______________ (1) The Company includes the shares underlying performance-based awards in the calculation of diluted earnings per share if the performance conditions have been satisfied as of the end of the reporting period and excludes such shares when the necessary conditions have not been met. The Company has included in the 2019, 2018 and 2017 calculations those shares that were contingently issuable upon the satisfaction of the performance conditions as of the end of the respective periods.

PROVISION FOR INCOME TAXES (Tab

PROVISION FOR INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
U.S. and foreign components of income before income taxes [Table Text Block]	U.S. and foreign components of income before income taxes were: Year Ended December 31, (in thousands) 2019 2018 2017 U.S. operations $ 82,692 $ (6,529 ) $ (6,944 ) Foreign operations 139,722 66,293 67,243 Total income before income taxes $ 222,414 $ 59,764 $ 60,299
Components of provision for income taxes [Table Text Block]	The components of the provision (benefit) for income taxes are as follows: Year Ended December 31, (in thousands) 2019 2018 2017 Current provision (benefit): Federal $ 18,293 $ (6,382 ) $ 35,311 State 184 4 4 Foreign 1,293 938 1,483 19,770 (5,440 ) 36,798 Deferred provision (benefit): Federal 9,683 (4,593 ) (3,640 ) State — — — Foreign (507 ) (187 ) (468 ) 9,176 (4,780 ) (4,108 ) Total $ 28,946 $ (10,220 ) $ 32,690
Effective income tax rate reconciliation [Table Text Block]	The provision (benefit) for income taxes differs from the amount that would result by applying the applicable federal income tax rate to income before income taxes, as follows: Year Ended December 31, 2019 2018 2017 Provision (benefit) computed at Federal statutory rate 21.0 % 21.0 % 35.0 % Business tax credits (2.4 ) (9.1 ) (5.7 ) Stock-based compensation (0.2 ) (2.2 ) (5.0 ) Foreign income taxed at different rate (12.7 ) (25.0 ) (37.3 ) GILTI inclusion 6.2 10.6 — U.S. Tax Act - transition tax 0.1 (16.2 ) 54.1 U.S. Tax Act - deferred tax asset and liability adjustment — — 8.1 Valuation allowance 0.8 2.8 2.2 Other 0.2 1.0 2.8 Total 13.0 % (17.1 )% 54.2 %
Components of net deferred income tax asset [Table Text Block]	The components of the net deferred income tax assets (liabilities) were as follows: December 31, (in thousands) 2019 2018 Deferred tax assets: Other reserves and accruals $ 3,099 $ 3,695 Tax credit carry-forwards 18,968 18,052 Stock compensation 1,644 3,050 Capital losses 157 157 Net operating loss 899 3,144 Other 1,000 — Valuation allowance (20,822 ) (19,955 ) 4,945 8,143 Deferred tax liabilities: Depreciation (2,273 ) (1,423 ) Other — (30 ) (2,273 ) (1,453 ) Net deferred tax assets $ 2,672 $ 6,690
Unrecognized tax benefits rollforward [Table Text Block]	Reconciliation of the beginning and ending amount of unrecognized tax benefits: (in thousands) Unrecognized Tax Benefits Unrecognized Tax Benefits Balance at January 1, 2017 $ 15,393 Gross Increase for Tax Positions of Current Year 1,699 Gross Decrease for Tax Positions of Prior Years (409 ) Unrecognized Tax Benefits Balance at December 31, 2017 16,683 Gross Increase for Tax Positions of Current Year 1,994 Gross Decrease for Tax Positions of Prior Years (70 ) Unrecognized Tax Benefits Balance at December 31, 2018 18,607 Gross Increase for Tax Positions of Current Year 1,379 Gross Decrease for Tax Positions of Prior Years (937 ) Unrecognized Tax Benefits Balance at December 31, 2019 $ 19,049

LEASES AND COMMITMENTS (Tables)

LEASES AND COMMITMENTS (Tables)	12 Months Ended
	Dec. 31, 2019
Leases and Commitments [Abstract]
Supplemental Balance Sheet Information of Operating Leases [Table Text Block]	Balance sheet information related to leases was as follows: (In thousands) Balance Sheet Classification December 31, Right-of-use assets Operating lease assets Other assets $ 9,521 Lease liabilities Current operating lease liabilities Other accrued liabilities $ 1,954 Non-current operating lease liabilities Other liabilities 7,031 Total $ 8,985
Lease Terms and Discount Rate [Table Text Block]	Lease term and discount rate December 31, Weighted average remaining lease term 4.8 years Weighted average discount rate 3.9 %
Supplemental Cash Flow Information Related to Leases [Table Text Block]	Supplemental cash flows information related to leases was as follow: Year-ended (In thousands) December 31, Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 2,964 Right-of-use assets obtained in exchange for new operating lease obligations $ 4,884
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	Future minimum lease payments under all non-cancelable lease agreements as of December 31, 2019, are as follows: (In thousands) December 31, 2020 $ 2,131 2021 2,313 2022 1,923 2023 1,690 2024 699 Thereafter 1,082 Total future minimum lease payments 9,838 Less imputed interest (853 ) Total $ 8,985

SELECTED QUARTERLY INFORMATION

SELECTED QUARTERLY INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information [Table Text Block]	The following tables set forth certain data from the Company's consolidated statements of income for each of the quarters in the years ended December 31, 2019 and 2018 . The unaudited quarterly consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements contained herein and include all adjustments that the Company considers necessary for a fair presentation of such information when read in conjunction with the Company’s annual audited consolidated financial statements and notes thereto appearing elsewhere in this report. The operating results for any quarter are not necessarily indicative of the results for any subsequent period or for the entire fiscal year. Three Months Ended (unaudited) Dec. 31, Sept. 30, June 30, Mar. 31, Dec. 31, Sept. 30, June 30, Mar. 31, (in thousands, except per share data) 2019 (1) 2019 2019 2019 2018 2018 2018 2018 Net revenues $ 114,457 $ 114,159 $ 102,865 $ 89,188 $ 93,307 $ 110,085 $ 109,482 $ 103,081 Gross profit 58,225 58,131 51,572 45,474 48,005 57,005 56,234 53,544 Net income $ 158,291 $ 17,099 $ 10,845 $ 7,233 $ 22,736 $ 17,667 $ 15,381 $ 14,200 Earnings per share Basic $ 5.38 $ 0.58 $ 0.37 $ 0.25 $ 0.78 $ 0.60 $ 0.52 $ 0.48 Diluted $ 5.28 $ 0.57 $ 0.37 $ 0.25 $ 0.77 $ 0.59 $ 0.51 $ 0.46 Shares used in per share calculation Basic 29,427 29,385 29,297 28,951 29,164 29,365 29,505 29,799 Diluted 30,005 29,866 29,702 29,446 29,651 29,998 30,183 30,552 _______________ (1) In October 2019 the Company entered into a favorable l itigation settlement with ON Semiconductor Corporation which resulted in a $169.0 million net gain (Refer to Note 13, Legal Proceedings and Contingencies , in our Notes to Consolidated Financial Statements included in this Annual Report on Form 10-K).

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts (Tables)	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule of Allowance for Ship and Debit [Table Text Block]	ollowing is a summary of the activity in the allowance for ship and debit credits: (in thousands) Balance at Beginning of Period Charged to Costs and Expenses Deductions (1) Balance at End of Period Allowance for ship and debit credits: Year ended December 31, 2017 $ 38,075 $ 273,492 $ (272,081 ) $ 39,486 Year ended December 31, 2018 $ 39,486 $ 242,068 $ (241,436 ) $ 40,118 Year ended December 31, 2019 $ 40,118 $ 230,278 $ (236,921 ) $ 33,475 _______________ (1) Deductions relate to ship and debit credits issued which adjust the sales price from the standard distribution price to the pre-approved lower price. Refer to Note 2, Significant Accounting Policies and Recent Accounting Pronouncements , for the Company’s revenue recognition policy, including the Company’s accounting for ship and debit claims.

SIGNIFICANT ACCOUNTING POLICI_3

SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS Segment Reporting (Details)	12 Months Ended
	Dec. 31, 2019segments
Segment Reporting [Abstract]
Number of Reportable Segments	1

SIGNIFICANT ACCOUNTING POLICI_4

SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Benefits Plan
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 1.4	$ 1.3	$ 1.2
Foreign Exchange Transactions
Foreign Currency Transaction Gain (Loss), before Tax	$ (0.3)	(0.1)	(0.1)
Warranty
Product Warranty Period	12 months
Advertising Expense
Advertising Expense	$ 1.4	$ 1.2	$ 1.3

SIGNIFICANT ACCOUNTING POLICI_5

SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS Recently Issued Accounting Pronouncements (Details) - Accounting Standards Update 2016-02 [Member] $ in Millions	Jan. 01, 2019USD ($)
Operating Lease, Right-of-Use Asset [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 7.3
Operating Lease, Liability [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 7.2

COMPONENTS OF THE COMPANY'S C_3

COMPONENTS OF THE COMPANY'S CONSOLIDATED BALANCE SHEETS Components of Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable
Accounts receivable trade	$ 61,036	$ 54,055
Accrued ship and debit	(33,475)	(40,118)
Allowance for stock rotation and rebate	(2,524)	(2,159)
Allowance for doubtful accounts	(763)	(706)
Total	24,274	11,072
Inventory, Net [Abstract]
Raw materials	39,058	41,138
Work-in-process	25,982	15,612
Finished goods	25,340	24,107
Total	90,380	80,857
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid income tax	5,615	3,081
Prepaid legal fees	16	181
Prepaid maintenance agreements	819	2,047
Advance to suppliers	3,579	2,157
Interest receivable	1,279	595
Other	4,289	3,854
Total	$ 15,597	$ 11,915

COMPONENTS OF THE COMPANY'S C_4

COMPONENTS OF THE COMPANY'S CONSOLIDATED BALANCE SHEETS Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	$ 317,020	$ 309,303
Accumulated depreciation	200,401	195,186
Depreciation	$ 19,190	$ 18,918	$ 18,374
Property and Equipment [Member] | Geographic Concentration Risk [Member]
Property, Plant and Equipment [Line Items]
Concentration Risk, Percentage	10.00%	10.00%	10.00%
Property and Equipment [Member] | Geographic Concentration Risk [Member] | United States of America
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	$ 160,700	$ 167,600	$ 159,500
Property and Equipment [Member] | Geographic Concentration Risk [Member] | THAILAND
Property, Plant and Equipment [Line Items]
Concentration Risk, Percentage	14.00%	12.00%	12.00%
Land
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	$ 21,790	$ 20,288
Construction-in-progress
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	18,604	21,696
Building and improvements
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	55,785	53,610
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	168,576	160,028
Computer software and hardware and office furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	$ 52,265	$ 53,681
Minimum [Member] | Building and improvements
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	4 years	4 years	4 years
Minimum [Member] | Machinery and equipment
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	2 years	2 years	2 years
Minimum [Member] | Computer software and hardware and office furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	4 years	4 years	4 years
Maximum [Member] | Building and improvements
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	40 years	40 years	40 years
Maximum [Member] | Machinery and equipment
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	8 years	8 years	8 years
Maximum [Member] | Computer software and hardware and office furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and Equipment, Useful Life	7 years	7 years	7 years

COMPONENTS OF THE COMPANY'S C_5

COMPONENTS OF THE COMPANY'S CONSOLIDATED BALANCE SHEETS Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss		$ (3,130)	$ (1,689)	$ (2,139)	$ (2,710)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(1,508)	326	374
Amounts reclassified from accumulated other comprehensive loss		67	124	197
Other Comprehensive Income (Loss), Net of Tax		(1,441)	450	571
Unrealized Gains and Losses on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss		583	(266)	(427)	(220)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		849	161	(207)
Amounts reclassified from accumulated other comprehensive loss		0	0	0
Other Comprehensive Income (Loss), Net of Tax		849	161	(207)
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss		(2,484)	(712)	(1,237)	(1,936)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(1,839)	401	502
Amounts reclassified from accumulated other comprehensive loss	[1]	67	124	197
Other Comprehensive Income (Loss), Net of Tax		(1,772)	525	699
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss		(1,229)	(711)	(475)	$ (554)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(518)	(236)	79
Amounts reclassified from accumulated other comprehensive loss		0	0	0
Other Comprehensive Income (Loss), Net of Tax		$ (518)	$ (236)	$ 79
[1]	This component of accumulated other comprehensive loss is included in the computation of net periodic pension cost for the years ended December 31, 2019 , 2018 and 2017 .

FAIR VALUE MEASUREMENTS (Detail

FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Investments as Fair Value	$ 382,336	$ 191,121
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Investments as Fair Value	2,983	304
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Investments as Fair Value	379,353	190,817
Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at Fair Value	232,398	94,451
Corporate securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at Fair Value	0	0
Corporate securities | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at Fair Value	232,398	94,451
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at Fair Value	146,955	96,366
Commercial paper | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at Fair Value	0	0
Commercial paper | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at Fair Value	146,955	96,366
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at Fair Value	2,983	304
Money market funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at Fair Value	2,983	304
Money market funds | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at Fair Value	$ 0	$ 0

MARKETABLE SECURITIES (Details)

MARKETABLE SECURITIES (Details) Securities in Thousands, $ in Thousands	Dec. 31, 2019USD ($)Securities	Dec. 31, 2018USD ($)Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 231,815	$ 94,717
Gross Unrealized Gains	589	2
Gross Unrealized Losses	(6)	(268)
Estimated Fair Market Value	$ 232,398	$ 94,451
Weighted Average Interest Rate on Investments	2.17%	2.65%
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | Securities	0	0
Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 15,934	$ 6,788
Gross Unrealized Gains	18	0
Gross Unrealized Losses	0	(2)
Estimated Fair Market Value	15,952	6,786
Investments due in 4-12 months:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	71,223	60,123
Gross Unrealized Gains	269	0
Gross Unrealized Losses	0	(244)
Estimated Fair Market Value	71,492	59,879
Investments due in 12 months or greater:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	144,658	27,806
Gross Unrealized Gains	302	2
Gross Unrealized Losses	(6)	(22)
Estimated Fair Market Value	144,954	27,786
Corporate securities | Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,934	6,788
Gross Unrealized Gains	18	0
Gross Unrealized Losses	0	(2)
Estimated Fair Market Value	15,952	6,786
Corporate securities | Investments due in 4-12 months:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	71,223	60,123
Gross Unrealized Gains	269	0
Gross Unrealized Losses	0	(244)
Estimated Fair Market Value	71,492	59,879
Corporate securities | Investments due in 12 months or greater:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	144,658	27,806
Gross Unrealized Gains	302	2
Gross Unrealized Losses	(6)	(22)
Estimated Fair Market Value	$ 144,954	$ 27,786

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets and Goodwill [Line Items]
Amortization of intangibles	$ 5,213	$ 5,267	$ 6,083
Intangible Assets, Net[Abstract]
Total intangible assets, Gross	61,177	60,251
Accumulated amortization	(44,312)	(39,099)
Total Finite Lived Intangible Assets, Net	15,604
Total Intangible Assets, Net	$ 16,865	21,152
Minimum [Member]
Intangible Assets and Goodwill [Line Items]
Useful life (in years)	2 years
Maximum [Member]
Intangible Assets and Goodwill [Line Items]
Useful life (in years)	12 years
Developed technology
Intangible Assets, Net[Abstract]
Finite-Lived Intangible Assets, Gross	$ 37,960	33,270
Accumulated amortization	(25,933)	(22,464)
Total Finite Lived Intangible Assets, Net	12,027	10,806
Customer relationships [Member]
Intangible Assets, Net[Abstract]
Finite-Lived Intangible Assets, Gross	20,030	20,030
Accumulated amortization	(18,098)	(16,520)
Total Finite Lived Intangible Assets, Net	1,932	3,510
Technology licenses [Member]
Intangible Assets, Net[Abstract]
Finite-Lived Intangible Assets, Gross	1,926	1,000
Accumulated amortization	(281)	(115)
Total Finite Lived Intangible Assets, Net	1,645	885
Domain name
Intangible Assets, Net[Abstract]
Indefinite-lived intangible assets	$ 1,261	1,261
In Process Research and Development [Member]
Intangible Assets, Net[Abstract]
Indefinite-lived intangible assets		$ 4,690

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS (Intangible Assets Amortization Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
In Process Research and Development Placed In Service	$ 4,700
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
2020	4,359
2021	3,494
2022	2,415
2023	2,173
2024	1,279
Thereafter	1,884
Total Finite Lived Intangible Assets, Net	15,604
Developed technology
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
Total Finite Lived Intangible Assets, Net	12,027	$ 10,806
Customer relationships [Member]
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
Total Finite Lived Intangible Assets, Net	1,932	3,510
Technology licenses [Member]
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
Total Finite Lived Intangible Assets, Net	1,645	885
Domain name
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 1,261	1,261
In Process Research and Development [Member]
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets		$ 4,690

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS Goodwill (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 91,849	$ 91,849

STOCK PLANS AND SHARE BASED C_3

STOCK PLANS AND SHARE BASED COMPENSATION (Details) shares in Millions	12 Months Ended
	Dec. 31, 2019USD ($)planspurchaseperiodsshares	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock-based compensation plans | plans	3
Number of shares available for future issuance | shares	2.1
Stock-based compensation expense | $	$ 23,347,000	$ 21,580,000	$ 24,677,000
2016 Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Issued | shares	0.8
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant | shares	1.7
Incentive Stock Options [Member] | 2007 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of stock options as percentage of fair market value on date of grant, minimum	100.00%
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period	4 years
Stock-based compensation expense | $	$ 17,500,000	16,600,000	15,200,000
Restricted Stock Units (RSUs) [Member] | Directors Equity Compensation Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Factor used to determine the number of options/units to be granted | $	$ 120,000
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum percentage of employee's compensation eligible for payroll deductions	15.00%
Purchase price of the purchase plan as percentage of the lower of the fair market value on the first day of each offering period or on the purchase date	85.00%
Number of purchase period in each offering period | purchaseperiods	1
Duration of each purchase period in each offering period	6 months
Shares reserved for issuance | shares	3.5
Number of shares purchased | shares	3.2
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant | shares	0.3
Stock-based compensation expense | $	$ 1,700,000	$ 1,600,000	$ 1,300,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period	4 years
Stock Options [Member] | 2007 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period	48 months
Awards expiration period, maximum	10 years
Stock Options [Member] | Directors Equity Compensation Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Factor used to determine the number of options/units to be granted | $	$ 120,000
Stock Options and Restricted Stock Units (RSUs) [Member] | Directors Equity Compensation Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Factor used to determine the number of options/units to be granted | $	$ 120,000

STOCK PLANS AND SHARE BASED C_4

STOCK PLANS AND SHARE BASED COMPENSATION (Stock-Based Compensation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	$ 23,347	$ 21,580	$ 24,677
Unrecognized compensation costs	37,111
Cost of revenues [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	1,237	1,097	1,321
Research and Development Expense [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	8,423	7,688	8,496
Selling and Marketing Expense [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	5,015	4,729	5,197
General and Administrative Expense [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	$ 8,672	8,066	9,663
Stock Options [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Awards vesting period	4 years
Performance Based Awards, Long-term and Short-term [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	$ 4,100	3,400	8,200
Long-Term Performance-based Awards [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Performance based period	3 years
Unrecognized compensation costs	$ 1,693
Unrecognized compensation costs, period of recognition (in years)	2 years
Number of performance-based awards shares released as a percentage of target number, minimum	0.00%
Number of performance-based awards shares released as a percentage of target number, maximum	200.00%
Restricted Stock Units (RSUs) [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Awards vesting period	4 years
Stock-based compensation expense	$ 17,500	16,600	15,200
Unrecognized compensation costs	$ 35,276
Unrecognized compensation costs, period of recognition (in years)	2 years 11 months 8 days
Employee Stock [Member]
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-based compensation expense	$ 1,700	$ 1,600	$ 1,300
Unrecognized compensation costs	$ 142
Unrecognized compensation costs, period of recognition (in years)	1 hour

STOCK PLANS AND SHARE BASED C_5

STOCK PLANS AND SHARE BASED COMPENSATION (Fair Value Assumptions) (Details) - Employee Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rates	2.28%	1.94%	0.91%
Expected volatility rates	37.00%	31.00%	30.00%
Expected dividend yield	0.91%	0.89%	0.80%
Expected term of purchase rights (in years)	15 days	15 days	15 days
Weighted-average estimated fair value of purchase rights	$ 19.39	$ 17.33	$ 16.74

STOCK PLANS AND SHARE BASED C_6

STOCK PLANS AND SHARE BASED COMPENSATION (Option Activity) (Details) - Stock Options [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Option activity under the Plans
Outstanding, shares, beginning of period	335	511	697
Outstanding, weighted-average exercise price, beginning of period (per share)	$ 32.41	$ 29.03	$ 28.62
Granted, shares	0	0	0
Granted, weighted-average exercise price (per share)	$ 0	$ 0	$ 0
Exercised, shares	(168)	(176)	(186)
Exercised, weighted-average exercise price (per share)	$ 25.96	$ 22.60	$ 27.48
Forfeited or expired, shares	0	0	0
Forfeited or expired, weighted-average exercise price (per share)	$ 0	$ 0	$ 0
Outstanding, shares, end of period	167	335	511
Outstanding, weighted-average exercise price, end of period (per share)	$ 38.88	$ 32.41	$ 29.03
Outstanding, weighted-average remaining contractual term (in years)	1 year 3 months 18 days
Outstanding, aggregate intrinsic value	$ 10,051
Vested and Exercisable, shares	167
Exercisable, weighted-average remaining contractual term (in years)	1 year 3 months 18 days
Exercisable, aggregate intrinsic value	$ 10,051
Total intrinsic value of options exercised	$ 8,300	$ 7,500	$ 8,900

STOCK PLANS AND SHARE BASED C_7

STOCK PLANS AND SHARE BASED COMPENSATION (Options by Exercise Price Range) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding | shares	167
Options Outstanding, Weighted Average Remaining Contractual Term (in years)	1 year 3 months 18 days
Options Outstanding, Weighted Average Exercise Price (per share)	$ 38.88
Options Vested and Exercisable, Number Vested | shares	167
Options Vested and Exercisable, Weighted Average Exercise Price (per share)	$ 38.88
$32.26 - $38.07
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options Outstanding, Exercise Price Range, Lower Range Limit	32.26
Options Outstanding, Exercise Price Range, Upper Range Limit	$ 38.07
Options Outstanding, Number Outstanding | shares	92
Options Outstanding, Weighted Average Remaining Contractual Term (in years)	8 months 26 days
Options Outstanding, Weighted Average Exercise Price (per share)	$ 36.80
Options Vested and Exercisable, Number Vested | shares	92
Options Vested and Exercisable, Weighted Average Exercise Price (per share)	$ 36.80
$39.49 - $42.88
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options Outstanding, Exercise Price Range, Lower Range Limit	39.49
Options Outstanding, Exercise Price Range, Upper Range Limit	$ 42.88
Options Outstanding, Number Outstanding | shares	75
Options Outstanding, Weighted Average Remaining Contractual Term (in years)	1 year 11 months 26 days
Options Outstanding, Weighted Average Exercise Price (per share)	$ 41.43
Options Vested and Exercisable, Number Vested | shares	75
Options Vested and Exercisable, Weighted Average Exercise Price (per share)	$ 41.43

STOCK PLANS AND SHARE BASED C_8

STOCK PLANS AND SHARE BASED COMPENSATION (Performance-based Awards and Restricted Stock Units) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Performance Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance-based awards shares released as a percentage of target number, minimum	0.00%
Number of performance-based awards shares released as a percentage of target number, maximum	200.00%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments [Roll Forward]
Outstanding, shares	61	26	79	99
Granted, shares	93	89	88
Vested, shares	(26)	(79)	(99)
Forfeited or expired, shares	(32)	(63)	(9)
Outstanding, weighted-average grant date fair value per share, beginning of period	$ 62.87	$ 63.99	$ 46.25
Granted, weighted-average grant date fair value per share	70.11	62.87	63.99
Vested, weighted-average grant date fair value per share	62.87	63.99	46.25
Forfeited or expired, weighted-average grant date fair value per share	70.11	62.87	63.99
Outstanding, weighted-average grant date fair value per share, end of period	$ 70.11	$ 62.87	$ 63.99
Outstanding, weighted-average remaining contractual term (in years)	0 years
Share Based Compensation Arrangement By Share Based Payment Award, Equity Instruments Other Than Options, Outstanding, Aggregate Intrinsic Value	$ 5,999
Outstanding and expected to vest, shares	61
Outstanding and expected to vest, weighted-average remaining contractual term (in years)	0 years
Outstanding and expected to vest, aggregate intrinsic value	$ 5,999
Grant date fair value of awards released	$ 1,600	$ 5,100	$ 4,600
Long-Term Performance-based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance-based awards shares released as a percentage of target number, minimum	0.00%
Number of performance-based awards shares released as a percentage of target number, maximum	200.00%
Performance based period	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments [Roll Forward]
Outstanding, shares	144	213	184	150
Granted, shares	72	72	71
Vested, shares	(70)	(38)	0
Forfeited or expired, shares	(71)	(5)	(37)
Outstanding, weighted-average grant date fair value per share, beginning of period	$ 55.48	$ 52.80	$ 47.65
Granted, weighted-average grant date fair value per share	68.17	59.90	63
Vested, weighted-average grant date fair value per share	43.26	52.45	0
Forfeited or expired, weighted-average grant date fair value per share	63	43.26	51.59
Outstanding, weighted-average grant date fair value per share, end of period	$ 64.05	$ 55.48	$ 52.80
Outstanding, weighted-average remaining contractual term (in years)	1 year 6 months
Outstanding, aggregate intrinsic value	$ 14,203
Outstanding and expected to vest, shares	58
Outstanding and expected to vest, weighted-average remaining contractual term (in years)	2 years
Outstanding and expected to vest, aggregate intrinsic value	$ 5,768
Grant date fair value of awards released	$ 3,000	$ 2,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments [Roll Forward]
Outstanding, shares	860	895	948	718
Granted, shares	291	275	558
Vested, shares	(301)	(296)	(284)
Forfeited or expired, shares	(25)	(32)	(44)
Outstanding, weighted-average grant date fair value per share, beginning of period	$ 58.19	$ 55.51	$ 47.54
Granted, weighted-average grant date fair value per share	69.79	62.85	60.82
Vested, weighted-average grant date fair value per share	56.19	53.78	46.52
Forfeited or expired, weighted-average grant date fair value per share	63.43	59.43	50.89
Outstanding, weighted-average grant date fair value per share, end of period	$ 62.66	$ 58.19	$ 55.51
Outstanding, weighted-average remaining contractual term (in years)	1 year 6 months 29 days
Share Based Compensation Arrangement By Share Based Payment Award, Equity Instruments Other Than Options, Outstanding, Aggregate Intrinsic Value	$ 85,037
Outstanding and expected to vest, shares	801
Outstanding and expected to vest, weighted-average remaining contractual term (in years)	1 year 6 months
Outstanding and expected to vest, aggregate intrinsic value	$ 79,192
Grant date fair value of awards released	$ 16,900	$ 15,900	$ 13,200
Exercise Price Range One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding, Exercise Price Range, Lower Range Limit	$ 32.26
Options Outstanding, Exercise Price Range, Upper Range Limit	38.07
Exercise Price Range Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding, Exercise Price Range, Lower Range Limit	39.49
Options Outstanding, Exercise Price Range, Upper Range Limit	$ 42.88

SIGNIFICANT CUSTOMERS AND GEO_3

SIGNIFICANT CUSTOMERS AND GEOGRAPHIC NET REVENUES (Customer and Credit Risk Concentration) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2019USD ($)customers	Dec. 31, 2018USD ($)customers	Dec. 31, 2017USD ($)customers
Concentration Risk [Line Items]
Revenues | $	$ 114,457	$ 114,159	$ 102,865	$ 89,188	$ 93,307	$ 110,085	$ 109,482	$ 103,081	$ 420,669	$ 415,955	$ 431,755
Distributors [Member]
Concentration Risk [Line Items]
Revenues | $									$ 304,600	$ 313,900	$ 330,900
Credit Concentration Risk | Accounts Receivable
Concentration Risk [Line Items]
Concentration risk percentage benchmark for total accounts receivable	10.00%				10.00%				10.00%	10.00%
Number of major customers | customers									10	10
Concentration Risk, Percentage									63.00%	64.00%
Credit Concentration Risk | Accounts Receivable | Powertech Distribution Ltd.
Concentration Risk [Line Items]
Concentration Risk, Percentage										17.00%
Credit Concentration Risk | Accounts Receivable | Powertech Distribution Ltd.
Concentration Risk [Line Items]
Concentration Risk, Percentage									10.00%	11.00%
Customer Concentration Risk | Revenue from Contract with Customer Benchmark [Member]
Concentration Risk [Line Items]
Number of major customers | customers									10	10	10
Concentration Risk, Percentage									10.00%	10.00%	10.00%
Concentration risk percentage of net revenue									54.00%	56.00%	54.00%
Customer Concentration Risk | Revenue from Contract with Customer Benchmark [Member] | Powertech Distribution Ltd.
Concentration Risk [Line Items]
Concentration risk percentage of net revenue									11.00%	14.00%	16.00%

SIGNIFICANT CUSTOMERS AND GEO_4

SIGNIFICANT CUSTOMERS AND GEOGRAPHIC NET REVENUES Geographic Net Revevnues (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Revenues by Geography [Line Items]
Revenues	$ 114,457	$ 114,159	$ 102,865	$ 89,188	$ 93,307	$ 110,085	$ 109,482	$ 103,081	$ 420,669	$ 415,955	$ 431,755
United States of America
Schedule of Revenues by Geography [Line Items]
Revenues									10,662	15,315	16,647
Hong Kong/China
Schedule of Revenues by Geography [Line Items]
Revenues									237,341	218,752	227,335
Taiwan
Schedule of Revenues by Geography [Line Items]
Revenues									36,297	43,081	50,307
Korea
Schedule of Revenues by Geography [Line Items]
Revenues									30,395	33,877	38,012
Western Europe (excluding Germany)
Schedule of Revenues by Geography [Line Items]
Revenues									36,025	49,834	48,230
Japan
Schedule of Revenues by Geography [Line Items]
Revenues									15,496	19,897	20,769
Germany
Schedule of Revenues by Geography [Line Items]
Revenues									20,197	14,403	11,558
Other
Schedule of Revenues by Geography [Line Items]
Revenues									$ 34,256	$ 20,796	$ 18,897

COMMON STOCK REPURCHASES AND _3

COMMON STOCK REPURCHASES AND CASH DIVIDENDS Common Stock Repurchases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 7,302	$ 103,154	$ 9,188
Common Stock [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount		$ 110,000	$ 30,000	$ 60,000
Stock Repurchased and Retired During Period, Shares	121,000	1,572,000	129,000
Stock Repurchased and Retired During Period, Value	$ 7,300	$ 103,200	$ 9,200
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 43,900

COMMON STOCK REPURCHASES AND _4

COMMON STOCK REPURCHASES AND CASH DIVIDENDS Cash Dividends (Details) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended												12 Months Ended
	Oct. 31, 2019quarters$ / shares	Jan. 31, 2019$ / shares	Dec. 31, 2019$ / shares	Sep. 30, 2019$ / shares	Jun. 30, 2019$ / shares	Mar. 31, 2019$ / shares	Dec. 31, 2018$ / shares	Sep. 30, 2018$ / shares	Jun. 30, 2018$ / shares	Mar. 31, 2018$ / shares	Dec. 31, 2017$ / shares	Sep. 30, 2017$ / shares	Jun. 30, 2017$ / shares	Mar. 31, 2017$ / shares	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Dividends Declared and Paid [Line Items]
Common Stock, Dividends, Per Share, Declared			$ 0.19	$ 0.17	$ 0.17	$ 0.17	$ 0.16	$ 0.16	$ 0.16	$ 0.16	$ 0.14	$ 0.14	$ 0.14	$ 0.14
Payments of Dividends | $															$ 20,506	$ 18,823	$ 16,634
Common Stock, Dividends, Per Share, Declared, Current Fiscal Year, Each Quarter		$ 0.17
Common Stock, Dividends, Number of Distributions Declared | quarters	5
Additional Common Stock, Dividends, Per Share, Declared, Current Fiscal Year, Fourth Quarter	$ 0.02
Common Stock, Dividends Per Share Declared, Current Fiscal Year, Fourth Quarter		$ 0.17
Common Stock, Dividends, Per Share, Declared, Next Fiscal Year, First Quarter	0.19
Common Stock, Dividends Per Share Declared, Next Fiscal Year, Second Quarter	0.19
Common Stock, Dividends Per Share Declared, Next Fiscal Year, Third Quarter	0.19
Common Stock, Dividends Per Share Declared, Next Fiscal Year, Fourth Quarter	$ 0.19

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended									12 Months Ended
		Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic earnings per share:
Net income		$ 158,291	[1]	$ 17,099	$ 10,845	$ 7,233	$ 22,736	$ 17,667	$ 15,381	$ 14,200	$ 193,468	$ 69,984	$ 27,609
Weighted-average common shares		29,427,000		29,385,000	29,297,000	28,951,000	29,164,000	29,365,000	29,505,000	29,799,000	29,267,000	29,456,000	29,674,000
Basic earnings per share		$ 5.38		$ 0.58	$ 0.37	$ 0.25	$ 0.78	$ 0.60	$ 0.52	$ 0.48	$ 6.61	$ 2.38	$ 0.93
Diluted earnings per share:
Net income		$ 158,291	[1]	$ 17,099	$ 10,845	$ 7,233	$ 22,736	$ 17,667	$ 15,381	$ 14,200	$ 193,468	$ 69,984	$ 27,609
Weighted-average common shares		29,427,000		29,385,000	29,297,000	28,951,000	29,164,000	29,365,000	29,505,000	29,799,000	29,267,000	29,456,000	29,674,000
Effect of dilutive securities:
Employee stock plans	[2]										549,000	691,000	871,000
Diluted weighted average common shares	[2]	30,005,000		29,866,000	29,702,000	29,446,000	29,651,000	29,998,000	30,183,000	30,552,000	29,816,000	30,147,000	30,545,000
Diluted earnings per share	[2]	$ 5.28		$ 0.57	$ 0.37	$ 0.25	$ 0.77	$ 0.59	$ 0.51	$ 0.46	$ 6.49	$ 2.32	$ 0.90
Antidilutive shares attributable to stock-based awards outstanding excluded from computation of diluted earnings per share											0	0	0
[1]	In October 2019 the Company entered into a favorable l itigation settlement with ON Semiconductor Corporation which resulted in a $169.0 million net gain (Refer to Note 13, Legal Proceedings and Contingencies , in our Notes to Consolidated Financial Statements included in this Annual Report on Form 10-K).
[2]	The Company includes the shares underlying performance-based awards in the calculation of diluted earnings per share if the performance conditions have been satisfied as of the end of the reporting period and excludes such shares when the necessary conditions have not been met. The Company has included in the 2019, 2018 and 2017 calculations those shares that were contingently issuable upon the satisfaction of the performance conditions as of the end of the respective periods.

PROVISION FOR INCOME TAXES (Det

PROVISION FOR INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Current Federal Tax Expense (Benefit) Related to Impact of Tax Cuts and Jobs Act		$ (9,700)	$ 37,500
U.S. and foreign components of income before income taxes [Abstract]
U.S. operations	$ 82,692	(6,529)	(6,944)
Foreign operations	139,722	66,293	67,243
INCOME BEFORE INCOME TAXES	222,414	59,764	60,299
Current provision:
Federal	18,293	(6,382)	35,311
State	184	4	4
Foreign	1,293	938	1,483
Current provision	19,770	(5,440)	36,798
Deferred provision (benefit):
Federal	9,683	(4,593)	(3,640)
State	0	0	0
Foreign	(507)	(187)	(468)
Deferred provision (benefit)	$ 9,176	$ (4,780)	$ (4,108)
Effective income tax rate reconciliation [Abstract]
Provision (benefit) computed at Federal statutory rate	21.00%	21.00%	35.00%
Business tax credits	(2.40%)	(9.10%)	(5.70%)
Stock-based compensation	(0.20%)	(2.20%)	(5.00%)
Foreign income taxed at different rate	(12.70%)	(25.00%)	(37.30%)
GILTI inclusion	6.20%	10.60%	0.00%
U.S. Tax Act - transition tax	0.10%	(16.20%)	54.10%
U.S. Tax Act - deferred tax asset and liability adjustment	0.00%	0.00%	8.10%
Valuation allowance	0.80%	2.80%	2.20%
Other	0.20%	1.00%	2.80%
Total	13.00%	(17.10%)	54.20%
Components of deferred income tax asset [Abstract]
Other reserves and accruals	$ 3,099	$ 3,695
Tax credit carry-forwards	18,968	18,052
Stock compensation	1,644	3,050
Capital losses	157	157
Net operating loss	899	3,144
Other	1,000	0
Valuation allowance	(20,822)	(19,955)
Deferred tax assets, net of valuation allowance	4,945	8,143
Depreciation	(2,273)	(1,423)
Other	0	(30)
Deferred tax liabilities	(2,273)	(1,453)
Net deferred tax asset	2,672	6,690
Reconciliation of the Beginning and Ending Amount of Unrecognized Tax Benefits [Roll Forward]
Unrecognized Tax Benefits, Balance at beginning of period	18,607	16,683	$ 15,393
Gross Increase for Tax Positions of Current Year	1,379	1,994	1,699
Gross Decrease for Tax Positions of Prior Years	(937)	(70)	(409)
Unrecognized Tax Benefits, Balance at end of period	19,049	18,607	16,683
Unrecognized tax benefits [Abstract]
Unrecognized Tax Benefits, Balance at end of period	19,049	18,607	$ 16,683
Income tax benefit that would be recorded if unrecognized tax benefits are recognized	10,600
Income tax interest and penalties accrued		$ 100
State and Local Jurisdiction [Member] | California Taxing Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	24,600
Research Tax Credit Carryforward [Member] | State and Local Jurisdiction [Member] | California Taxing Authority [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	27,500
Research Tax Credit Carryforward [Member] | State and Local Jurisdiction [Member] | New Jersey Division of Taxation [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	700
Research Tax Credit Carryforward [Member] | Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	$ 3,100
Earliest Tax Year [Member] | State and Local Jurisdiction [Member] | California Taxing Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Jan. 1, 2031
Earliest Tax Year [Member] | Research Tax Credit Carryforward [Member] | State and Local Jurisdiction [Member] | New Jersey Division of Taxation [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Expiration Date	Jan. 1, 2026
Earliest Tax Year [Member] | Research Tax Credit Carryforward [Member] | Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Expiration Date	Jan. 1, 2030

LEASES AND COMMITMENTS Leases E

LEASES AND COMMITMENTS Leases Expense and Balance Sheet Information of Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Operating Lease, Expense	$ 2,500	$ 2,200	$ 2,000
Operating Lease, Right-of-Use Asset	9,521
Operating Lease, Liability, Current	1,954
Operating Lease, Liability, Noncurrent	7,031
Operating Lease, Liability	$ 8,985

LEASES AND COMMITMENTS Lease Te

LEASES AND COMMITMENTS Lease Terms and Discount Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Operating Lease, Expense	$ 2.5	$ 2.2	$ 2
Lease Terms and Discount Rate [Line Items]
Lessee, Operating Lease, Option Extension Term, Maximum	6 years
Operating Lease, Weighted Average Remaining Lease Term	4 years 9 months 18 days
Lessee, Operating Lease, Option To Terminate, Minimum Term	1 year
Lessee, Operating Lease, Discount Rate	3.90%
Maximum [Member]
Lease Terms and Discount Rate [Line Items]
Lesee Operating Lease Remaining Lease Term Range	9 years
Minimum [Member]
Lease Terms and Discount Rate [Line Items]
Lesee Operating Lease Remaining Lease Term Range	1 year

LEASES AND COMMITMENTS Suppleme

LEASES AND COMMITMENTS Supplemental Cash Flows Information Regarding Operating Leases (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ 2,964
Right-of-use assets obtained in exchange for new operating lease obligations	$ 4,884

LEASES AND COMMITMENTS Maturiti

LEASES AND COMMITMENTS Maturities of Operating Lease Liabilities (Details) $ in Thousands	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 2,131
2021	2,313
2022	1,923
2023	1,690
2024	699
Thereafter	1,082
Total future minimum lease payments	9,838
Less imputed interest	853
Total	$ 8,985

LEASES AND COMMITMENTS Commitme

LEASES AND COMMITMENTS Commitments (Details)	Dec. 31, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
Unrecorded Unconditional Purchase Obligation	$ 0

LEGAL PROCEEDINGS AND CONTING_2

LEGAL PROCEEDINGS AND CONTINGENCIES (Details) $ in Thousands	Jan. 06, 2020patentspatent	Apr. 01, 2016patent	Feb. 28, 2019USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Gain and Loss Contingencies [Line Items]
Proceeds from Legal Settlements				$ 175,000
Litigation settlement				168,969	$ 0	$ 0
Pending Litigation [Member] | Patent Infringement Claim One [Member]
Gain and Loss Contingencies [Line Items]
Loss Contingency, Damages Awarded, Value			$ 6,700	$ 1,200
Loss Contingency, Patents Allegedly Infringed, Number | patent		1
Subsequent Event [Member] | Pending Litigation [Member] | Patent Infringement Claim Two [Member]
Gain and Loss Contingencies [Line Items]
Gain Contingency, Patents Allegedly Infringed upon, Number | patent	2
Subsequent Event [Member] | Pending Litigation [Member] | Patent Infringement Claim Two Counterclaim [Member]
Gain and Loss Contingencies [Line Items]
Loss Contingency, Patents Allegedly Infringed, Number | patents	3

RETIREMENT PLANS (Details)

RETIREMENT PLANS (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	$ 6.6	$ 3.8
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	8.2	6.4
Business Acquisition, Purchase Price Allocation, Projected Benefit Obligation (Asset), Net of Plan Assets Acquired	14.8	10.2
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	0.4
Defined Benefit Pension Items
Defined Benefit Plan Disclosure [Line Items]
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	$ 2.5	$ 0.7	$ 1.2

BANK LINE OF CREDIT (Details)

BANK LINE OF CREDIT (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jul. 27, 2016
Line of Credit Facility [Line Items]
Credit Agreement, maximum borrowing capacity		$ 75
Letters of Credit Outstanding, Amount	$ 6.2
Line of credit, amount outstanding	$ 0
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Credit Agreement, maximum borrowing capacity		$ 20

SELECTED QUARTERLY INFORMATIO_2

SELECTED QUARTERLY INFORMATION (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended									12 Months Ended
		Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenues		$ 114,457		$ 114,159	$ 102,865	$ 89,188	$ 93,307	$ 110,085	$ 109,482	$ 103,081	$ 420,669	$ 415,955	$ 431,755
Gross Profit		58,225		58,131	51,572	45,474	48,005	57,005	56,234	53,544	213,402	214,788	213,664
Net income (loss)		$ 158,291	[1]	$ 17,099	$ 10,845	$ 7,233	$ 22,736	$ 17,667	$ 15,381	$ 14,200	193,468	69,984	27,609
Litigation settlement											$ 168,969	$ 0	$ 0
Earnings per share
Basic		$ 5.38		$ 0.58	$ 0.37	$ 0.25	$ 0.78	$ 0.60	$ 0.52	$ 0.48	$ 6.61	$ 2.38	$ 0.93
Diluted	[2]	$ 5.28		$ 0.57	$ 0.37	$ 0.25	$ 0.77	$ 0.59	$ 0.51	$ 0.46	$ 6.49	$ 2.32	$ 0.90
Shares used in per share calculation
Basic		29,427		29,385	29,297	28,951	29,164	29,365	29,505	29,799	29,267	29,456	29,674
Diluted	[2]	30,005		29,866	29,702	29,446	29,651	29,998	30,183	30,552	29,816	30,147	30,545
[1]	In October 2019 the Company entered into a favorable l itigation settlement with ON Semiconductor Corporation which resulted in a $169.0 million net gain (Refer to Note 13, Legal Proceedings and Contingencies , in our Notes to Consolidated Financial Statements included in this Annual Report on Form 10-K).
[2]	The Company includes the shares underlying performance-based awards in the calculation of diluted earnings per share if the performance conditions have been satisfied as of the end of the reporting period and excludes such shares when the necessary conditions have not been met. The Company has included in the 2019, 2018 and 2017 calculations those shares that were contingently issuable upon the satisfaction of the performance conditions as of the end of the respective periods.

Schedule II - Valuation and Q_3

Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Ship and Debit Credits [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		$ 40,118	$ 39,486	$ 38,075
Charged to Costs and Expenses		230,278	242,068	273,492
Deductions	[1]	(236,921)	(241,436)	(272,081)
Balance at End of Period		$ 33,475	$ 40,118	$ 39,486
[1]	Deductions relate to ship and debit credits issued which adjust the sales price from the standard distribution price to the pre-approved lower price. Refer to Note 2, Significant Accounting Policies and Recent Accounting Pronouncements , for the Company’s revenue recognition policy, including the Company’s accounting for ship and debit claims.