Monolithic Power Systems (MPWR) 10-Q 11 May 20 2020 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 04, 2020
Document Information [Line Items]
Entity Central Index Key	0001280452
Entity Registrant Name	MONOLITHIC POWER SYSTEMS INC
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2020
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	000-51026
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0466789
Entity Address, Address Line One	5808 Lake Washington Blvd. NE
Entity Address, City or Town	Kirkland
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	98033
City Area Code	425
Local Phone Number	296-9956
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	MPWR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		44,740,000

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 154,880	$ 172,960
Short-term investments	334,386	282,437
Accounts receivable, net	54,341	52,704
Inventories	131,499	127,500
Other current assets	29,679	19,605
Total current assets	704,785	655,206
Property and equipment, net	236,807	228,315
Long-term investments	3,057	3,138
Goodwill	6,571	6,571
Deferred tax assets, net	13,821	17,193
Other long-term assets	42,463	45,952
Total assets	1,007,504	956,375
Current liabilities:
Accounts payable	37,752	27,271
Accrued compensation and related benefits	18,633	26,164
Other accrued liabilities	56,110	44,790
Total current liabilities	112,495	98,225
Income tax liabilities	37,596	37,596
Other long-term liabilities	44,223	47,063
Total liabilities	194,314	182,884
Commitments and contingencies
Stockholders’ equity:
Common stock and additional paid-in capital: $0.001 par value; shares authorized: 150,000; shares issued and outstanding: 44,715 and 43,616, respectively	581,736	549,517
Retained earnings	241,465	229,450
Accumulated other comprehensive loss	(10,011)	(5,476)
Total stockholders’ equity	813,190	773,491
Total liabilities and stockholders’ equity	$ 1,007,504	$ 956,375

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - $ / shares shares in Thousands	Mar. 31, 2020	Dec. 31, 2019
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	150,000	150,000
Common stock, shares issued (in shares)	44,715	43,616
Common stock, shares outstanding (in shares)	44,715	43,616

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue	$ 165,778	$ 141,363
Cost of revenue	74,331	63,357
Gross profit	91,447	78,006
Operating expenses:
Research and development	25,956	25,458
Selling, general and administrative	32,164	30,553
Litigation expense	2,341	278
Total operating expenses	60,461	56,289
Income from operations	30,986	21,717
Other income (expense), net	(1,714)	3,341
Income before income taxes	29,272	25,058
Income tax benefit	(6,484)	(1,123)
Net income	$ 35,756	$ 26,181
Net income per share
Basic (in dollars per share)	$ 0.80	$ 0.61
Diluted (in dollars per share)	$ 0.77	$ 0.58
Weighted-average shares outstanding:
Basic (in shares)	44,455	42,749
Diluted (in shares)	46,670	45,232

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net income	$ 35,756	$ 26,181
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(2,882)	3,677
Change in unrealized gain (loss) on available-for-sale securities, net of tax of $55 and $(98), respectively	(1,653)	826
Other comprehensive income (loss), net of tax	(4,535)	4,503
Comprehensive income	$ 31,221	$ 30,684

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parentheticals) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Change in unrealized gain (loss) on available-for-sale securities, tax	$ 55	$ (98)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common Stock Including Additional Paid in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2018	42,505
Balance at Dec. 31, 2018	$ 450,908	$ 194,728	$ (5,543)	$ 640,093
Net income	0	26,181	0	26,181
Other comprehensive income (loss)	0	0	4,503	4,503
Dividends and dividend equivalents declared	$ 0	(18,531)	0	(18,531)
Common stock issued under the employee equity incentive plan (in shares)	514
Common stock issued under the employee equity incentive plan	$ 10,383	0	0	10,383
Common stock issued under the employee stock purchase plan (in shares)	14
Common stock issued under the employee stock purchase plan	$ 1,627	0	0	1,627
Stock-based compensation expense	$ 15,995	0	0	15,995
Balance (in shares) at Mar. 31, 2019	43,033
Balance at Mar. 31, 2019	$ 478,913	202,378	(1,040)	$ 680,251
Balance (in shares) at Dec. 31, 2019	43,616			43,616
Balance at Dec. 31, 2019	$ 549,517	229,450	(5,476)	$ 773,491
Net income	0	35,756	0	35,756
Other comprehensive income (loss)	0	0	(4,535)	(4,535)
Dividends and dividend equivalents declared	$ 0	(23,741)	0	(23,741)
Common stock issued under the employee equity incentive plan (in shares)	1,084
Common stock issued under the employee equity incentive plan	$ 11,758	0	0	11,758
Common stock issued under the employee stock purchase plan (in shares)	15
Common stock issued under the employee stock purchase plan	$ 1,892	0	0	1,892
Stock-based compensation expense	$ 18,569	0	0	$ 18,569
Balance (in shares) at Mar. 31, 2020	44,715			44,715
Balance at Mar. 31, 2020	$ 581,736	$ 241,465	$ (10,011)	$ 813,190

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (Parentheticals) - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Dividends and dividend equivalents declared per share (in dollars per share)	$ 0.50	$ 0.40

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 35,756	$ 26,181
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,328	3,255
(Gain) loss on disposal and sale of property and equipment, net	(1)	14
Amortization of premium on available-for-sale securities	494	121
(Gain) loss on deferred compensation plan investments	3,750	(1,935)
Deferred taxes, net	3,412	(33)
Stock-based compensation expense	18,562	16,010
Changes in operating assets and liabilities:
Accounts receivable	(1,635)	(3,676)
Inventories	(3,994)	(6,171)
Other assets	(10,061)	(1,576)
Accounts payable	7,185	4,778
Accrued compensation and related benefits	(7,374)	4
Income tax liabilities	34	(1,491)
Other accrued liabilities	963	3,355
Net cash provided by operating activities	51,419	38,836
Cash flows from investing activities:
Purchases of property and equipment	(9,952)	(58,376)
Acquisition of in-place leases	0	(981)
Purchases of short-term investments	(101,566)	0
Proceeds from maturities and sales of short-term investments	47,397	28,076
Proceeds from sales of long-term investments	100	0
Proceeds from sales of property and equipment	1	1,456
Contributions to deferred compensation plan, net	(438)	(956)
Net cash used in investing activities	(64,458)	(30,781)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(279)	(10)
Proceeds from common stock issued under the employee equity incentive plan	11,758	10,383
Proceeds from common stock issued under the employee stock purchase plan	1,892	1,627
Dividends and dividend equivalents paid	(17,427)	(12,761)
Net cash used in financing activities	(4,056)	(761)
Effect of change in exchange rates	(985)	1,770
Net increase (decrease) in cash, cash equivalents and restricted cash	(18,080)	9,064
Cash, cash equivalents and restricted cash, beginning of period	173,076	172,818
Cash, cash equivalents and restricted cash, end of period	154,996	181,882
Supplemental disclosures for cash flow information:
Cash paid for taxes	279	393
Non-cash investing and financing activities:
Liability accrued for property and equipment purchases	10,909	958
Liability accrued for dividends and dividend equivalents	$ 23,725	$ 18,534

Note 1 - Basis of Presentation

Note 1 - Basis of Presentation	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	1. The accompanying unaudited condensed consolidated financial statements have been prepared by Monolithic Power Systems, Inc. (the “Company” or “MPS”) in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) have been condensed or omitted in accordance with these accounting principles, rules and regulations. The information in this report should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Annual Report on Form 10 December 31, 2019, February 28, 2020. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the Company’s financial position, results of operations and cash flows for the interim periods presented. The financial statements contained in this Form 10 not may December 31, 2020 Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions used in these condensed consolidated financial statements primarily include those related to revenue recognition, inventory valuation, valuation of share-based awards, contingencies and income tax valuation allowances. The coronavirus pandemic first December 2019 ( 19” 2020, not 10 December 31, 2019. may may Recently Adopted Accounting Pronouncement s In August 2018, No. 2018 13, Fair Value Measurement (Topic 820 3 first 2020 not In January 2017, No. 2017 04, Intangibles – Goodwill and Other (Topic 350 two not first 2020 not In June 2016, No. 2016 13, Financial Instruments – Credit Losses (Topic 326 first 2020, not Recent Accounting Pronouncem ent Not March 31, 2020 In December 2019, No. 2019 12, Income Taxes (Topic 740 ): Simplifying the Accounting for Income Taxes, December 15, 2020.

Note 2 - Revenue Recognition

Note 2 - Revenue Recognition	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Revenue from Contract with Customer [Text Block]	2. Revenue from Product Sales The Company generates revenue primarily from product sales, which include assembled and tested integrated circuits (“ICs”), as well as dies in wafer form. These product sales were 98% and 99% of the Company’s total revenue for the three March 31, 2020 2019, third not 7 The Company sells its products primarily through third three March 31, 2020 2019, not The Company recognizes revenue when it satisfies a performance obligation by transferring control of the promised goods or services to its customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. The Company excludes taxes assessed by government authorities, such as sales taxes, from revenue. Product sales consist of a single performance obligation that the Company satisfies at a point in time. The Company recognizes product revenue from distributors and direct end customers when the following events have occurred: (a) the Company has transferred physical possession of the products, (b) the Company has a present right to payment, (c) the customer has legal title to the products, and (d) the customer bears significant risks and rewards of ownership of the products. In accordance with the shipping terms specified in the contracts, these criteria are generally met when the products are shipped from the Company’s facilities (such as the “Ex Works” shipping term) or delivered to the customers’ locations (such as the “Delivered Duty Paid” shipping term). Under certain consignment agreements, revenue is not not Variable Consideration The Company accounts for price adjustment and stock rotation rights as variable consideration that reduces the transaction price and recognizes that reduction in the same period the associated revenue is recognized. Three U.S.-based distributors have price adjustment rights when they sell the Company’s products to their end customers at a price that is lower than the distribution price invoiced by the Company. When the Company receives claims from the distributors that products have been sold to the end customers at the lower price, the Company issues the distributors credit memos for the price adjustments. The Company estimates the price adjustments using the expected value method based on an analysis of historical claims, at both the distributor and product level, as well as an assessment of any known trends of product sales mix. Other U.S. distributors and non-U.S. distributors, which make up the majority of the Company’s total sales to distributors, do not Certain distributors have limited stock rotation rights that permit the return of a small percentage of the previous six Contract Balances Accounts Receivable: The Company records a receivable when it has an unconditional right to receive consideration after the performance obligations are satisfied. As of March 31, 2020 December 31, 2019, 30 60 not may three March 31, 2020 2019, not March 31, 2020, not December 31, 2019, not Contract Liabilities: For certain customers located in Asia, the Company requires cash payments two March 31, 2020 December 31, 2019, three March 31, 2020 three March 31, 2020, December 31, 2019. Practical Expedients The Company has elected the practical expedient to expense sales commissions as incurred because the amortization period would have been one The Company’s standard payment terms generally require customers to pay 30 to 60 days after the Company satisfies the performance obligations. For those customers who are required to pay in advance, the Company satisfies the performance obligations generally within a quarter. The Company has elected not The Company’s unsatisfied performance obligations primarily include products held in consignment arrangements and customer purchase orders for products that the Company has not one not

Note 3 - Stock-based Compensati

Note 3 - Stock-based Compensation	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Share-based Payment Arrangement [Text Block]	3. 2014 “2014 The Board of Directors adopted the 2014 April 2013, June 2013. October 2014, 2014 2014 November 13, 2014 2014 November 13, 2024. March 31, 2020, 2014 Stock-Based Compensation Expense The Company recognized stock-based compensation expenses as follows (in thousands): Three Months Ended March 31, 2020 2019 Cost of revenue $ 557 $ 531 Research and development 4,370 4,429 Selling, general and administrative 13,635 11,050 Total stock-based compensation expense $ 18,562 $ 16,010 Tax benefit related to stock-based compensation (1) $ 470 $ 838 _________________ ( 1 Amounts reflect the tax benefit related to stock-based compensation recorded for equity awards that are expected to generate tax deductions when they vest in future periods. Restricted Stock Units (“RSUs”) The Company’s RSUs include time-based RSUs, RSUs with performance conditions (“PSUs”), RSUs with market conditions (“MSUs”), and RSUs with both market and performance conditions (“MPSUs”). Vesting of awards with performance conditions or market conditions is subject to the achievement of pre-determined performance goals and the approval of such achievement by the Compensation Committee of the Board of Directors (the “Compensation Committee”). All awards include service conditions which require continued employment with the Company. A summary of RSU activity is presented in the table below (in thousands, except per-share amounts): Time-Based RSUs PSUs and MPSUs MSUs Total Number of Shares Weighted-Average Grant Date Fair Value Per Share Number of Shares Weighted-Average Grant Date Fair Value Per Share Number of Shares Weighted-Average Grant Date Fair Value Per Share Number of Shares Weighted-Average Grant Date Fair Value Per Share Outstanding at January 1, 2020 180 $ 115.45 1,987 $ 74.50 1,886 $ 37.63 4,053 $ 59.16 Granted 47 $ 183.53 324 (1) $ 168.69 - $ - 371 $ 170.56 Vested (24 ) $ 104.06 (979 ) $ 56.22 (81 ) $ 23.57 (1,084 ) $ 54.85 Forfeited (2 ) $ 114.71 (7 ) $ 81.64 (3 ) $ 68.48 (12 ) $ 83.20 Outstanding at March 31, 2020 201 $ 132.71 1,325 $ 110.99 1,802 $ 38.21 3,328 $ 72.88 ( 1 Amount reflects the number of awards that may The intrinsic value related to vested RSUs was $182.1 million and $57.7 million for the three March 31, 2020 2019, March 31, 2020, March 31, 2020, three Cash proceeds from vested PSUs with a purchase price totaled $11.8 million and $10.4 million for the three March 31, 2020 2019, Time-Based RSUs: For the three March 31, 2020, four one 2020 PSUs: In February 2020, two 2020 2021 two “2020 2020 2020 first 2022 2020 two 2020 In February 2020, 2021 two 2020 2021 two “2020 2020 2020 first 2022 2020 two 2020 The 2020 2020 $30 20 $30 2004 For the three March 31, 2020 2019, March 31, 2020, The intrinsic value of the shares issued was $1.0 million and $0.3 million for the three March 31, 2020 2019, March 31, 2020, third 2020. Three Months Ended March 31, 2020 2019 Expected term (in years) 0.5 0.5 Expected volatility 31.4 % 37.3 % Risk-free interest rate 1.6 % 2.5 % Dividend yield 1.1 % 1.2 % Cash proceeds from the shares issued under the ESPP were $1.9 million and $1.6 million for the three March 31, 2020 2019,

Note 4 - Balance Sheet Componen

Note 4 - Balance Sheet Components	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Supplemental Balance Sheet Disclosures [Text Block]	4. Inventories Inventories consist of the following (in thousands): March 31, December 31, 2020 2019 Raw materials $ 32,502 $ 22,872 Work in process 48,022 42,681 Finished goods 50,975 61,947 Total $ 131,499 $ 127,500 Other Current Assets Other current assets consist of the following (in thousands): March 31, December 31, 2020 2019 RSU tax withholding proceeds receivable $ 5,744 $ 6,106 Prepaid expense 18,444 7,991 Accrued interest receivable 2,530 2,490 Assets for product returns 1,824 1,585 Other 1,137 1,433 Total $ 29,679 $ 19,605 Other Long-Term Assets Other long-term assets consist of the following (in thousands): March 31, December 31, 2020 2019 Deferred compensation plan assets $ 35,547 $ 38,858 Operating lease right-of-use (“ROU”) assets 2,744 2,863 Prepaid expense 2,715 2,687 Other 1,457 1,544 Total $ 42,463 $ 45,952 Other Accrued Liabilities Other accrued liabilities consist of the following (in thousands): March 31, December 31, 2020 2019 Dividends and dividend equivalents $ 27,846 $ 21,747 Stock rotation and sales returns 6,474 5,530 Accrued purchases of property and equipment 5,834 4,678 Income tax payable 2,462 2,435 Customer prepayments 5,221 3,412 Commissions 2,191 1,425 Operating lease liabilities 1,140 1,254 Warranty 1,144 1,139 Other 3,798 3,170 Total $ 56,110 $ 44,790 Other Long-Term Liabilities Other long-term liabilities consist of the following (in thousands): March 31, December 31, 2020 2019 Deferred compensation plan liabilities $ 36,627 $ 39,665 Dividend equivalents 6,481 6,265 Operating lease liabilities 1,086 1,103 Other 29 30 Total $ 44,223 $ 47,063

Note 5 - Leases

Note 5 - Leases	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Leases Disclosure [Text Block]	5. Lessee The Company has operating leases primarily for administrative and sales and marketing offices, manufacturing operations and research and development facilities, employee housing units and certain equipment. These leases have remaining lease terms from less than a four five not As of March 31, 2020 December 31, 2019, March 31, 2020 December 31, 2019, Three Months Ended March 31, 2020 2019 Lease costs: Operating lease costs $ 366 $ 305 Short-term and other lease costs 77 98 Total lease costs $ 443 $ 403 Three Months Ended March 31, 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 373 $ 304 ROU assets obtained in exchange for new operating lease liabilities (1) $ 277 $ 2,264 March 31, December 31, 2020 2019 Weighted-average remaining lease term (in years) 2.2 2.1 Weighted-average discount rate 3.6 % 3.7 % ( 1 For the three March 31, 2019, January 1, 2019. As of March 31, 2020, 2020 (remaining nine months) $ 994 2021 774 2022 453 2023 96 2024 12 Total remaining lease payments 2,329 Less: imputed interest (103 ) Total lease liabilities $ 2,226 Reported as: Current liabilities $ 1,140 Long-term liabilities $ 1,086 Lessor The Company owns certain office buildings and leases a portion of these properties to third one five five For the three March 31, 2020 2019, March 31, 2020, 2020 (remaining nine months) $ 1,620 2021 2,285 2022 2,074 2023 1,240 2024 552 Thereafter 59 Total $ 7,830

Note 6 - Net Income Per Share

Note 6 - Net Income Per Share	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Earnings Per Share [Text Block]	6 . NET INCOME PER SHARE Basic net income per share is computed by dividing net income by the weighted-average number of common shares outstanding for the period. Diluted net income per share reflects the potential dilution that would occur if outstanding securities or other contracts to issue common stock were exercised or converted into common shares, and calculated using the treasury stock method. Contingently issuable shares, including equity awards with performance conditions or market conditions, are considered outstanding common shares and included in the basic net income per share as of the date that all necessary conditions to earn the awards have been satisfied. Prior to the end of the contingency period, the number of contingently issuable shares included in the diluted net income per share is based on the number of shares, if any, that would be issuable under the terms of the arrangement at the end of the reporting period. The Company’s RSUs contain forfeitable rights to receive cash dividend equivalents, which are accumulated and paid to the employees when the underlying RSUs vest. Dividend equivalents accumulated on the underlying RSUs are forfeited if the employees do not not not The following table sets forth the computation of basic and diluted net income per share (in thousands, except per-share amounts): Three Months Ended March 31, 2020 2019 Numerator: Net income $ 35,756 $ 26,181 Denominator: Weighted-average outstanding shares - basic 44,455 42,749 Effect of dilutive securities 2,215 2,483 Weighted-average outstanding shares - diluted 46,670 45,232 Net income per share: Basic $ 0.80 $ 0.61 Diluted $ 0.77 $ 0.58 Anti-dilutive common stock equivalents were not

Note 7 - Segment, Significant C

Note 7 - Segment, Significant Customers and Geographic Information	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Segment Reporting Disclosure [Text Block]	7 . SEGMENT , SIGNIFICANT CUSTOMERS AND GEOGRAPHIC INFORMATION The Company operates in one The Company sells its products primarily through third 10% 10% Revenue Accounts Receivable Three Months Ended March 31, March 31, December 31, Customer 2020 2019 2020 2019 Distributor A 23 % 23 % 28 % 24 % Distributor B * * 13 % 11 % Value-added reseller A * * 16 % 13 % Direct customer A 10 % * * * * Represents less than 10%. The Company’s agreements with these third may may not The following is a summary of revenue by geographic regions (in thousands): Three Months Ended March 31, Country or Region 2020 2019 China $ 105,737 $ 76,198 Taiwan 16,540 21,347 Europe 13,072 12,984 South Korea 10,944 9,611 Southeast Asia 8,780 8,672 Japan 6,890 6,642 United States 3,737 5,806 Other 78 103 Total $ 165,778 $ 141,363 The following is a summary of revenue by product family (in thousands): Three Months Ended March 31, Product Family 2020 2019 DC to DC $ 156,875 $ 132,711 Lighting Control 8,903 8,652 Total $ 165,778 $ 141,363 The following is a summary of property and equipment, net, by geographic regions (in thousands): March 31, December 31, Country 2020 2019 China $ 119,904 $ 113,888 United States 96,982 94,671 Taiwan 17,341 17,652 Other 2,580 2,104 Total $ 236,807 $ 228,315

Note 8 - Commitments and Contin

Note 8 - Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Commitments and Contingencies Disclosure [Text Block]	8 . COMMITMENTS AND CONTINGENCIES Product Warranties The Company generally provides one two no not The changes in warranty reserves are as follows (in thousands): Three Months Ended March 31, 2020 2019 Balance at beginning of period $ 1,139 $ 4,564 Warranty provision for product sales 541 268 Settlements made (111 ) (2,271 ) Unused warranty provision (425 ) (516 ) Balance at end of period $ 1,144 $ 2,045 Purchase Commitments The Company has outstanding purchase commitments with its suppliers and other parties that require the future purchases of goods or services, which primarily consist of wafer and other inventory purchases, assembly and other manufacturing services, construction or purchases of property and equipment, and license arrangements. As of March 31, 2020, Litigation The Company is a party to actions and proceedings in the ordinary course of business, including potential litigation initiated by its stockholders, challenges to the enforceability or validity of its intellectual property, claims that the Company’s products infringe on the intellectual property rights of others, and employment matters. These proceedings often involve complex questions of fact and law and may March 31, 2020, no

Note 9 - Cash, Cash Equivalents

Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Financial Instruments Disclosure [Text Block]	9 . CASH, CASH EQUIVALENTS, INVESTMENTS AND RESTRICTED CASH The following is a summary of the Company’s cash, cash equivalents and investments (in thousands): March 31, December 31, 2020 2019 Cash, cash equivalents and investments: Cash $ 143,926 $ 144,860 Money market funds 10,954 28,100 Corporate debt securities 308,909 260,950 Commercial paper 4,943 1,994 U.S. treasuries and government agency bonds 20,534 19,493 Auction-rate securities backed by student-loan notes 3,057 3,138 Total $ 492,323 $ 458,535 March 31, December 31, 2020 2019 Reported as: Cash and cash equivalents $ 154,880 $ 172,960 Short-term investments 334,386 282,437 Long-term investments 3,057 3,138 Total $ 492,323 $ 458,535 The following table summarizes the contractual maturities of the short-term and long-term available-for-sale investments as of March 31, 2020 ( Amortized Cost Fair Value Due in less than 1 year $ 175,874 $ 175,281 Due in 1 - 5 years 159,928 159,105 Due in greater than 5 years 3,220 3,057 Total $ 339,022 $ 337,443 Realized gains and losses recognized on the sale of the available-for-sale investments were not The following tables summarize the unrealized gain and loss positions related to the available-for sale investments (in thousands): March 31, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Money market funds $ 10,954 $ - $ - $ 10,954 Corporate debt securities 310,367 559 (2,017 ) 308,909 Commercial paper 4,942 3 (2 ) 4,943 U.S. treasuries and government agency bonds 20,493 41 - 20,534 Auction-rate securities backed by student-loan notes 3,220 - (163 ) 3,057 Total $ 349,976 $ 603 $ (2,182 ) $ 348,397 December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Money market funds $ 28,100 $ - $ - $ 28,100 Corporate debt securities 260,645 383 (78 ) 260,950 Commercial paper 1,994 - - 1,994 U.S. treasuries and government agency bonds 19,487 7 (1 ) 19,493 Auction-rate securities backed by student-loan notes 3,320 - (182 ) 3,138 Total $ 313,546 $ 390 $ (261 ) $ 313,675 The following tables present information about the available-for-sale investments that had been in a continuous unrealized loss position for less than 12 12 March 31, 2020 Less than 12 Months Greater than 12 Months Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 215,069 $ (2,017 ) $ - $ - $ 215,069 $ (2,017 ) Commercial paper 2,469 (2 ) - - 2,469 (2 ) Auction-rate securities backed by student-loan notes - - 3,057 (163 ) 3,057 (163 ) Total $ 217,538 $ (2,019 ) $ 3,057 $ (163 ) $ 220,595 $ (2,182 ) December 31, 2019 Less than 12 Months Greater than 12 Months Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 82,126 $ (63 ) $ 11,136 $ (15 ) $ 93,262 $ (78 ) U.S. treasuries and government agency bonds 993 (1 ) - - 993 (1 ) Auction-rate securities backed by student-loan notes - - 3,138 (182 ) 3,138 (182 ) Total $ 83,119 $ (64 ) $ 14,274 $ (197 ) $ 97,393 $ (261 ) An impairment exists when the fair value of an investment is less than its amortized cost basis. As of March 31, 2020, not December 31, 2019, not one not The Company’s auction-rate securities are backed by pools of student loans supported by guarantees by the U.S. Department of Education. The underlying maturities of these securities are up to 26 years. The Company has received all scheduled interest payments on a timely basis pursuant to the terms and conditions of the securities. The Company does not not not Restricted Cash March 31, December 31, 2020 2019 Cash and cash equivalents $ 154,880 $ 172,960 Restricted cash included in other long-term assets 116 116 Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows $ 154,996 $ 173,076 As of March 31, 2020 December 31, 2019,

Note 10 - Fair Value Measuremen

Note 10 - Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Fair Value Disclosures [Text Block]	10 . FAIR VALUE MEASUREMENTS The following tables summarize the fair value measurement of the financial assets (in thousands): March 31, 2020 Total Level 1 Level 2 Level 3 Money market funds $ 10,954 $ 10,954 $ - $ - Corporate debt securities 308,909 - 308,909 - Commercial paper 4,943 - 4,943 - U.S. treasuries and government agency bonds 20,534 - 20,534 - Auction-rate securities backed by student-loan notes 3,057 - - 3,057 Mutual funds and money market funds under deferred compensation plan 20,226 20,226 - - Total $ 368,623 $ 31,180 $ 334,386 $ 3,057 December 31, 2019 Total Level 1 Level 2 Level 3 Money market funds $ 28,100 $ 28,100 $ - $ - Corporate debt securities 260,950 - 260,950 - Commercial paper 1,994 - 1,994 - U.S. treasuries and government agency bonds 19,493 - 19,493 - Auction-rate securities backed by student-loan notes 3,138 - - 3,138 Mutual funds and money market funds under deferred compensation plan 21,975 21,975 - - Total $ 335,650 $ 50,075 $ 282,437 $ 3,138 ● Level 1—includes ● Level 2—includes may third ● Level 3—includes The Company’s level 3 Balance at January 1, 2020 $ 3,138 Change in unrealized gain included in other comprehensive income 19 Sale and settlement at par (100 ) Balance at March 31, 2020 $ 3,057 The Company determined the fair value of the auction-rate securities using a discounted cash flow model with the following assumptions: March 31, 2020 (1) December 31, 2019 Time-to-liquidity (in years) 2 - 3 (2.5) 2 - 3 Discount rate 3.1% - 7.3% (5.0%) 4.0% - 8.3% ( 1 The parenthetical value represents the weighted average, which was calculated based on the relative fair value of the securities. The fair value measurement involves the analysis of valuation techniques and evaluation of unobservable inputs commonly used by market participants to price similar instruments. Outputs from the valuation process are assessed against various market sources when they are available, including marketplace quotes, recent trades of similar illiquid securities and independent pricing services. The valuation of the auction-rate securities is subject to significant management judgment regarding projected future cash flows, which will depend on many factors, including the quality of the underlying collateral, estimated time to liquidity including potential to be called or restructured, underlying final maturity, and market conditions, among others. Changes in any of the unobservable inputs used in the fair value measurement of auction-rate securities in isolation would result in a lower or higher fair value measurement. For example, an increase in the time-to-liquidity assumption or estimated discount rate would result in a lower fair value measurement.

Note 11 - Deferred Compensation

Note 11 - Deferred Compensation Plan	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Compensation and Employee Benefit Plans [Text Block]	11 . DEFERRED COMPENSATION PLAN The following table summarizes the deferred compensation plan balances on the Condensed Consolidated Balance Sheets (in thousands): March 31, December 31, 2020 2019 Deferred compensation plan asset components: Cash surrender value of corporate-owned life insurance policies $ 15,321 $ 16,883 Fair value of mutual funds and money market funds 20,226 21,975 Total $ 35,547 $ 38,858 Deferred compensation plan assets reported in: Other long-term assets $ 35,547 $ 38,858 Deferred compensation plan liabilities reported in: Accrued compensation and related benefits (short-term) $ 155 $ 425 Other long-term liabilities 36,627 39,665 Total $ 36,782 $ 40,090

Note 12 - Other Income (Expense

Note 12 - Other Income (Expense), Net	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Other Nonoperating Income and Expense [Text Block]	12 . OTHER INCOME (EXPENSE) , NET The components of other income (expense), net, are as follows (in thousands): Three Months Ended March 31, 2020 2019 Interest income $ 2,374 $ 1,696 Amortization of premium on available-for-sale securities (494 ) (121 ) Gain (loss) on deferred compensation plan investments (3,750 ) 1,935 Foreign currency exchange gain (loss) 3 (201 ) Other 153 32 Total $ (1,714 ) $ 3,341

Note 13 - Income Taxes

Note 13 - Income Taxes	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Income Tax Disclosure [Text Block]	13 . INCOME TAXES The income tax provision or benefit for interim periods is generally determined using an estimate of the Company’s annual effective tax rate and adjusted for discrete items, if any, in the relevant period. Each quarter the estimate of the annual effective tax rate is updated, and if the Company’s estimated tax rate changes, a cumulative adjustment is made. In March 2020, 19 not December 31, 2020. The income tax benefit for the three March 31, 2020 The income tax benefit for the three March 31, 2019 The Company’s uncertain tax positions relate to the allocation of income and deductions among its global entities and to the determination of the research and development tax credit. Various events, some of which cannot be predicted, such as clarification of tax law by administrative or judicial means, may twelve not July 2015, Altera Corp. v. Commissioner, December 2015, June 2016. June 2019, July 2019, November 2019, February 2020, not March 31, 2020.

Note 14 - Accumulated Other Com

Note 14 - Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Comprehensive Income (Loss) Note [Text Block]	14 . ACCUMULATED OTHER COMPREHENSIVE LOSS The following table summarizes the changes in accumulated other comprehensive loss (in thousands): Unrealized Gains (Losses) on Available-for-Sale Securities Foreign Currency Translation Adjustments Total Balance as of January 1, 2020 $ 135 $ (5,611 ) $ (5,476 ) Other comprehensive loss before reclassifications (1,680 ) (2,882 ) (4,562 ) Amounts reclassified from accumulated other comprehensive loss (28 ) - (28 ) Tax effect 55 - 55 Net current period other comprehensive loss (1,653 ) (2,882 ) (4,535 ) Balance as of March 31, 2020 $ (1,518 ) $ (8,493 ) $ (10,011 ) The amounts reclassified from accumulated other comprehensive loss were recorded in other income (expense), net, on the Condensed Consolidated Statements of Operations.

Note 15 - Dividends and Dividen

Note 15 - Dividends and Dividend Equivalents	3 Months Ended
	Mar. 31, 2020
Notes to Financial Statements
Dividends And Dividend Equivalents [Text Block]	15 . DIVIDENDS AND DIVIDEND EQUIVALENTS Cash Dividend Program The Company has a dividend program approved by the Board of Directors, pursuant to which the Company intends to pay quarterly cash dividends on its common stock. Based on the Company’s historical practice, stockholders of record as of the last business day of the quarter are entitled to receive the quarterly cash dividends when and if declared by the Board of Directors, which are payable to the stockholders in the following month. The Board of Directors declared the following cash dividends (in thousands, except per-share amounts): Three Months Ended March 31, 2020 2019 Dividend declared per share $ 0.50 $ 0.40 Total amount $ 22,317 $ 17,180 As of March 31, 2020 December 31, 2019, The declaration of any future cash dividends is at the discretion of the Board of Directors and will depend on, among other things, the Company’s financial condition, results of operations, capital requirements, business conditions, and other factors that the Board of Directors may The Company anticipates that cash used for future dividend payments will come from its domestic cash, cash generated from ongoing U.S. operations, and cash repatriated from its Bermuda subsidiary. Earnings from other foreign subsidiaries will continue to be indefinitely reinvested. Cash Dividend Equivalent Rights The Company's RSUs contain rights to receive cash dividend equivalents, which entitle employees who hold RSUs to the same dividend value per share as holders of common stock. The dividend equivalents are accumulated and paid to the employees when the underlying RSUs vest. Dividend equivalents accumulated on the underlying RSUs are forfeited if the employees do not not March 31, 2020 December 31, 2019,

Significant Accounting Policies

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Use of Estimates, Policy [Policy Text Block]	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions used in these condensed consolidated financial statements primarily include those related to revenue recognition, inventory valuation, valuation of share-based awards, contingencies and income tax valuation allowances. The coronavirus pandemic first December 2019 ( 19” 2020, not 10 December 31, 2019. may may
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting Pronouncement s In August 2018, No. 2018 13, Fair Value Measurement (Topic 820 3 first 2020 not In January 2017, No. 2017 04, Intangibles – Goodwill and Other (Topic 350 two not first 2020 not In June 2016, No. 2016 13, Financial Instruments – Credit Losses (Topic 326 first 2020, not Recent Accounting Pronouncem ent Not March 31, 2020 In December 2019, No. 2019 12, Income Taxes (Topic 740 ): Simplifying the Accounting for Income Taxes, December 15, 2020.

Note 3 - Stock-based Compensa_2

Note 3 - Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Share-based Payment Arrangement, Cost by Plan [Table Text Block]	Three Months Ended March 31, 2020 2019 Cost of revenue $ 557 $ 531 Research and development 4,370 4,429 Selling, general and administrative 13,635 11,050 Total stock-based compensation expense $ 18,562 $ 16,010 Tax benefit related to stock-based compensation (1) $ 470 $ 838
Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block]	Time-Based RSUs PSUs and MPSUs MSUs Total Number of Shares Weighted-Average Grant Date Fair Value Per Share Number of Shares Weighted-Average Grant Date Fair Value Per Share Number of Shares Weighted-Average Grant Date Fair Value Per Share Number of Shares Weighted-Average Grant Date Fair Value Per Share Outstanding at January 1, 2020 180 $ 115.45 1,987 $ 74.50 1,886 $ 37.63 4,053 $ 59.16 Granted 47 $ 183.53 324 (1) $ 168.69 - $ - 371 $ 170.56 Vested (24 ) $ 104.06 (979 ) $ 56.22 (81 ) $ 23.57 (1,084 ) $ 54.85 Forfeited (2 ) $ 114.71 (7 ) $ 81.64 (3 ) $ 68.48 (12 ) $ 83.20 Outstanding at March 31, 2020 201 $ 132.71 1,325 $ 110.99 1,802 $ 38.21 3,328 $ 72.88
Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]	Three Months Ended March 31, 2020 2019 Expected term (in years) 0.5 0.5 Expected volatility 31.4 % 37.3 % Risk-free interest rate 1.6 % 2.5 % Dividend yield 1.1 % 1.2 %

Note 4 - Balance Sheet Compon_2

Note 4 - Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Schedule of Inventory, Current [Table Text Block]	March 31, December 31, 2020 2019 Raw materials $ 32,502 $ 22,872 Work in process 48,022 42,681 Finished goods 50,975 61,947 Total $ 131,499 $ 127,500
Schedule of Other Current Assets [Table Text Block]	March 31, December 31, 2020 2019 RSU tax withholding proceeds receivable $ 5,744 $ 6,106 Prepaid expense 18,444 7,991 Accrued interest receivable 2,530 2,490 Assets for product returns 1,824 1,585 Other 1,137 1,433 Total $ 29,679 $ 19,605
Schedule of Other Assets, Noncurrent [Table Text Block]	March 31, December 31, 2020 2019 Deferred compensation plan assets $ 35,547 $ 38,858 Operating lease right-of-use (“ROU”) assets 2,744 2,863 Prepaid expense 2,715 2,687 Other 1,457 1,544 Total $ 42,463 $ 45,952
Schedule of Accrued Liabilities [Table Text Block]	March 31, December 31, 2020 2019 Dividends and dividend equivalents $ 27,846 $ 21,747 Stock rotation and sales returns 6,474 5,530 Accrued purchases of property and equipment 5,834 4,678 Income tax payable 2,462 2,435 Customer prepayments 5,221 3,412 Commissions 2,191 1,425 Operating lease liabilities 1,140 1,254 Warranty 1,144 1,139 Other 3,798 3,170 Total $ 56,110 $ 44,790
Other Noncurrent Liabilities [Table Text Block]	March 31, December 31, 2020 2019 Deferred compensation plan liabilities $ 36,627 $ 39,665 Dividend equivalents 6,481 6,265 Operating lease liabilities 1,086 1,103 Other 29 30 Total $ 44,223 $ 47,063

Note 5 - Leases (Tables)

Note 5 - Leases (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Lease, Cost [Table Text Block]	Three Months Ended March 31, 2020 2019 Lease costs: Operating lease costs $ 366 $ 305 Short-term and other lease costs 77 98 Total lease costs $ 443 $ 403 Three Months Ended March 31, 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 373 $ 304 ROU assets obtained in exchange for new operating lease liabilities (1) $ 277 $ 2,264 March 31, December 31, 2020 2019 Weighted-average remaining lease term (in years) 2.2 2.1 Weighted-average discount rate 3.6 % 3.7 %
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	2020 (remaining nine months) $ 994 2021 774 2022 453 2023 96 2024 12 Total remaining lease payments 2,329 Less: imputed interest (103 ) Total lease liabilities $ 2,226 Reported as: Current liabilities $ 1,140 Long-term liabilities $ 1,086
Lessor, Operating Lease, Payment to be Received, Fiscal Year Maturity [Table Text Block]	2020 (remaining nine months) $ 1,620 2021 2,285 2022 2,074 2023 1,240 2024 552 Thereafter 59 Total $ 7,830

Note 6 - Net Income Per Share (

Note 6 - Net Income Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	Three Months Ended March 31, 2020 2019 Numerator: Net income $ 35,756 $ 26,181 Denominator: Weighted-average outstanding shares - basic 44,455 42,749 Effect of dilutive securities 2,215 2,483 Weighted-average outstanding shares - diluted 46,670 45,232 Net income per share: Basic $ 0.80 $ 0.61 Diluted $ 0.77 $ 0.58

Note 7 - Segment, Significant_2

Note 7 - Segment, Significant Customers and Geographic Information (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Schedules of Concentration of Risk, by Risk Factor [Table Text Block]	Revenue Accounts Receivable Three Months Ended March 31, March 31, December 31, Customer 2020 2019 2020 2019 Distributor A 23 % 23 % 28 % 24 % Distributor B * * 13 % 11 % Value-added reseller A * * 16 % 13 % Direct customer A 10 % * * *
Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area [Table Text Block]	Three Months Ended March 31, Country or Region 2020 2019 China $ 105,737 $ 76,198 Taiwan 16,540 21,347 Europe 13,072 12,984 South Korea 10,944 9,611 Southeast Asia 8,780 8,672 Japan 6,890 6,642 United States 3,737 5,806 Other 78 103 Total $ 165,778 $ 141,363
Revenue from External Customers by Products and Services [Table Text Block]	Three Months Ended March 31, Product Family 2020 2019 DC to DC $ 156,875 $ 132,711 Lighting Control 8,903 8,652 Total $ 165,778 $ 141,363
Schedule of Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries by Country [Table Text Block]	March 31, December 31, Country 2020 2019 China $ 119,904 $ 113,888 United States 96,982 94,671 Taiwan 17,341 17,652 Other 2,580 2,104 Total $ 236,807 $ 228,315

Note 8 - Commitments and Cont_2

Note 8 - Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Schedule of Product Warranty Liability [Table Text Block]	Three Months Ended March 31, 2020 2019 Balance at beginning of period $ 1,139 $ 4,564 Warranty provision for product sales 541 268 Settlements made (111 ) (2,271 ) Unused warranty provision (425 ) (516 ) Balance at end of period $ 1,144 $ 2,045

Note 9 - Cash, Cash Equivalen_2

Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Fair Value, by Balance Sheet Grouping [Table Text Block]	March 31, December 31, 2020 2019 Cash, cash equivalents and investments: Cash $ 143,926 $ 144,860 Money market funds 10,954 28,100 Corporate debt securities 308,909 260,950 Commercial paper 4,943 1,994 U.S. treasuries and government agency bonds 20,534 19,493 Auction-rate securities backed by student-loan notes 3,057 3,138 Total $ 492,323 $ 458,535 March 31, December 31, 2020 2019 Reported as: Cash and cash equivalents $ 154,880 $ 172,960 Short-term investments 334,386 282,437 Long-term investments 3,057 3,138 Total $ 492,323 $ 458,535
Investments Classified by Contractual Maturity Date [Table Text Block]	Amortized Cost Fair Value Due in less than 1 year $ 175,874 $ 175,281 Due in 1 - 5 years 159,928 159,105 Due in greater than 5 years 3,220 3,057 Total $ 339,022 $ 337,443
Unrealized Gain (Loss) on Investments [Table Text Block]	March 31, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Money market funds $ 10,954 $ - $ - $ 10,954 Corporate debt securities 310,367 559 (2,017 ) 308,909 Commercial paper 4,942 3 (2 ) 4,943 U.S. treasuries and government agency bonds 20,493 41 - 20,534 Auction-rate securities backed by student-loan notes 3,220 - (163 ) 3,057 Total $ 349,976 $ 603 $ (2,182 ) $ 348,397 December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Money market funds $ 28,100 $ - $ - $ 28,100 Corporate debt securities 260,645 383 (78 ) 260,950 Commercial paper 1,994 - - 1,994 U.S. treasuries and government agency bonds 19,487 7 (1 ) 19,493 Auction-rate securities backed by student-loan notes 3,320 - (182 ) 3,138 Total $ 313,546 $ 390 $ (261 ) $ 313,675
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table Text Block]	March 31, 2020 Less than 12 Months Greater than 12 Months Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 215,069 $ (2,017 ) $ - $ - $ 215,069 $ (2,017 ) Commercial paper 2,469 (2 ) - - 2,469 (2 ) Auction-rate securities backed by student-loan notes - - 3,057 (163 ) 3,057 (163 ) Total $ 217,538 $ (2,019 ) $ 3,057 $ (163 ) $ 220,595 $ (2,182 ) December 31, 2019 Less than 12 Months Greater than 12 Months Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 82,126 $ (63 ) $ 11,136 $ (15 ) $ 93,262 $ (78 ) U.S. treasuries and government agency bonds 993 (1 ) - - 993 (1 ) Auction-rate securities backed by student-loan notes - - 3,138 (182 ) 3,138 (182 ) Total $ 83,119 $ (64 ) $ 14,274 $ (197 ) $ 97,393 $ (261 )
Restrictions on Cash and Cash Equivalents [Table Text Block]	March 31, December 31, 2020 2019 Cash and cash equivalents $ 154,880 $ 172,960 Restricted cash included in other long-term assets 116 116 Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows $ 154,996 $ 173,076

Note 10 - Fair Value Measurem_2

Note 10 - Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	March 31, 2020 Total Level 1 Level 2 Level 3 Money market funds $ 10,954 $ 10,954 $ - $ - Corporate debt securities 308,909 - 308,909 - Commercial paper 4,943 - 4,943 - U.S. treasuries and government agency bonds 20,534 - 20,534 - Auction-rate securities backed by student-loan notes 3,057 - - 3,057 Mutual funds and money market funds under deferred compensation plan 20,226 20,226 - - Total $ 368,623 $ 31,180 $ 334,386 $ 3,057 December 31, 2019 Total Level 1 Level 2 Level 3 Money market funds $ 28,100 $ 28,100 $ - $ - Corporate debt securities 260,950 - 260,950 - Commercial paper 1,994 - 1,994 - U.S. treasuries and government agency bonds 19,493 - 19,493 - Auction-rate securities backed by student-loan notes 3,138 - - 3,138 Mutual funds and money market funds under deferred compensation plan 21,975 21,975 - - Total $ 335,650 $ 50,075 $ 282,437 $ 3,138
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	Balance at January 1, 2020 $ 3,138 Change in unrealized gain included in other comprehensive income 19 Sale and settlement at par (100 ) Balance at March 31, 2020 $ 3,057
Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]	March 31, 2020 (1) December 31, 2019 Time-to-liquidity (in years) 2 - 3 (2.5) 2 - 3 Discount rate 3.1% - 7.3% (5.0%) 4.0% - 8.3%

Note 11 - Deferred Compensati_2

Note 11 - Deferred Compensation Plan (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits by Title of Individual and Type of Deferred Compensation [Table Text Block]	March 31, December 31, 2020 2019 Deferred compensation plan asset components: Cash surrender value of corporate-owned life insurance policies $ 15,321 $ 16,883 Fair value of mutual funds and money market funds 20,226 21,975 Total $ 35,547 $ 38,858 Deferred compensation plan assets reported in: Other long-term assets $ 35,547 $ 38,858 Deferred compensation plan liabilities reported in: Accrued compensation and related benefits (short-term) $ 155 $ 425 Other long-term liabilities 36,627 39,665 Total $ 36,782 $ 40,090

Note 12 - Other Income (Expen_2

Note 12 - Other Income (Expense), Net (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Schedule of Other Nonoperating Income (Expense) [Table Text Block]	Three Months Ended March 31, 2020 2019 Interest income $ 2,374 $ 1,696 Amortization of premium on available-for-sale securities (494 ) (121 ) Gain (loss) on deferred compensation plan investments (3,750 ) 1,935 Foreign currency exchange gain (loss) 3 (201 ) Other 153 32 Total $ (1,714 ) $ 3,341

Note 14 - Accumulated Other C_2

Note 14 - Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Unrealized Gains (Losses) on Available-for-Sale Securities Foreign Currency Translation Adjustments Total Balance as of January 1, 2020 $ 135 $ (5,611 ) $ (5,476 ) Other comprehensive loss before reclassifications (1,680 ) (2,882 ) (4,562 ) Amounts reclassified from accumulated other comprehensive loss (28 ) - (28 ) Tax effect 55 - 55 Net current period other comprehensive loss (1,653 ) (2,882 ) (4,535 ) Balance as of March 31, 2020 $ (1,518 ) $ (8,493 ) $ (10,011 )

Note 15 - Dividends and Divid_2

Note 15 - Dividends and Dividend Equivalents (Tables)	3 Months Ended
	Mar. 31, 2020
Notes Tables
Dividends Declared [Table Text Block]	Three Months Ended March 31, 2020 2019 Dividend declared per share $ 0.50 $ 0.40 Total amount $ 22,317 $ 17,180

Note 2 - Revenue Recognition (D

Note 2 - Revenue Recognition (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Lapse Period for Consignment (Day)	60 days
Accounts Receivable, after Allowance for Credit Loss, Current, Total	$ 54,341		$ 52,704
Accounts Receivable, Allowance for Credit Loss, Writeoff	0	$ 0
Accounts Receivable, Allowance for Credit Loss, Ending Balance	0		0
Contract with Customer, Liability, Current	5,221		3,412
Contract with Customer, Liability, Revenue Recognized	$ 3,200
Minimum [Member]
Contract with Customer, Payment Term (Day)	30 days
Maximum [Member]
Contract with Customer, Payment Term (Day)	60 days
Certain Customers in China [Member]
Contract with Customer, Payment Term Required Prior to Shipping Products (Week)	14 days
Certain Customers in China [Member] | Accrued Liabilities, Current [Member]
Contract with Customer, Liability, Current	$ 5,200		$ 3,400
Customer Concentration Risk [Member] | Revenue Benchmark [Member]
Concentration Risk, Percentage	80.00%	84.00%
Product [Member]
Percentage of Revenue	98.00%	99.00%

Note 3 - Stock-based Compensa_3

Note 3 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Feb. 29, 2020	Mar. 31, 2020	Mar. 31, 2019	Nov. 13, 2014
Proceeds, Issuance of Shares, Share-based Payment Arrangement, Excluding Option Exercised		$ 11,758	$ 10,383
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)		371,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)		$ 170.56
Proceeds from Stock Plans		$ 1,892	1,627
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested		182,100	57,700
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding		$ 517,600
Share Price (in dollars per share)		$ 167.46
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total		$ 144,100
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)		3 years
Proceeds, Issuance of Shares, Share-based Payment Arrangement, Excluding Option Exercised		$ 11,800	$ 10,400
Time-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)		47,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)		$ 183.53
Time-Based RSUs [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		4 years
Time-Based RSUs [Member] | Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		1 year
PSU 2020 [Member]
Share Price (in dollars per share)	$ 182.62
Share-based Compensation Arrangement by Share-based Payment Award, Price Per Share Payable Upon Vesting of Equity Instruments Other than Options (in dollars per share)	30
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)	$ 182.62
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (Year)	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	33.60%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	1.40%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	1.10%
PSU 2020 [Member] | Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	100,000
Share-based Compensation Arrangement by Share-based Payment Award, Vesting, Measurement Period of Relative Revenue Growth Rate to Industry Average (Year)	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Maximum Percentage Allowed	300.00%
Maximum Stock Compensation Costs	$ 51,100
PSU 2020 [Member] | Executive Officer [Member] | Vesting First Quarter of 2022 if Performance Conditions are Met [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	50.00%
PSU 2020 [Member] | Executive Officer [Member] | Vesting Over Two Years Following First Quarter of 2022 on Quarterly Basis [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	50.00%
PSU 2020 [Member] | Non-Executive Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	30,000
Share-based Compensation Arrangement by Share-based Payment Award, Vesting, Measurement Period of Relative Revenue Growth Rate to Industry Average (Year)	2 years
Maximum Stock Compensation Costs	$ 12,900
PSU 2020 [Member] | Non-Executive Employees [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Minimum Percentage Allowed	200.00%
PSU 2020 [Member] | Non-Executive Employees [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Maximum Percentage Allowed	300.00%
PSU 2020 [Member] | Non-Executive Employees [Member] | Vesting First Quarter of 2020 if Performance Conditions are Met [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	50.00%
PSU 2020 [Member] | Non-Executive Employees [Member] | Vesting Over Two Years Following First Quarter of 2022 on Quarterly Basis [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	50.00%
The2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)				5,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)		1,200,000
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)		4,500,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total		$ 400
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)		15,000	14,000
Employee Stock Purchase Plan Shares Issued, Intrinsic Value		$ 1,000	$ 300
Proceeds from Stock Plans		$ 1,900	$ 1,600

Note 3 - Stock-based Compensa_4

Note 3 - Stock-based Compensation - Stock-based Compensation Plan Expenses (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Share based compensation expense		$ 18,562	$ 16,010
Tax benefit related to stock-based compensation	[1]	470	838
Cost of Sales [Member]
Share based compensation expense		557	531
Research and Development Expense [Member]
Share based compensation expense		4,370	4,429
Selling, General and Administrative Expenses [Member]
Share based compensation expense		$ 13,635	$ 11,050
[1]	Amounts reflect the tax benefit related to stock-based compensation recorded for equity awards that are expected to generate tax deductions when they vest in future periods.

Note 3 - Stock-based Compensa_5

Note 3 - Stock-based Compensation - RSU Summary (Details)	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Beginning balance (in shares) | shares	4,053,000
Weighted-Average Grant Date Fair Value Per Share, beginning balance (in dollars per share) | $ / shares	$ 59.16
Granted (in shares) | shares	371,000
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) | $ / shares	$ 170.56
Vested (in shares) | shares	(1,084,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) | $ / shares	$ 54.85
Forfeited (in shares) | shares	(12,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) | $ / shares	$ 83.20
Ending balance (in shares) | shares	3,328,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 72.88
Time-Based RSUs [Member]
Beginning balance (in shares) | shares	180,000
Weighted-Average Grant Date Fair Value Per Share, beginning balance (in dollars per share) | $ / shares	$ 115.45
Granted (in shares) | shares	47,000
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) | $ / shares	$ 183.53
Vested (in shares) | shares	(24,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) | $ / shares	$ 104.06
Forfeited (in shares) | shares	(2,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) | $ / shares	$ 114.71
Ending balance (in shares) | shares	201,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 132.71
PSUs and MPSUs [Member]
Beginning balance (in shares) | shares	1,987,000
Weighted-Average Grant Date Fair Value Per Share, beginning balance (in dollars per share) | $ / shares	$ 74.50
Granted (in shares) | shares	324,000	[1]
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) | $ / shares	$ 168.69
Vested (in shares) | shares	(979,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) | $ / shares	$ 56.22
Forfeited (in shares) | shares	(7,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) | $ / shares	$ 81.64
Ending balance (in shares) | shares	1,325,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 110.99
MSUs [Member]
Beginning balance (in shares) | shares	1,886,000
Weighted-Average Grant Date Fair Value Per Share, beginning balance (in dollars per share) | $ / shares	$ 37.63
Granted (in shares) | shares	0
Weighted-Average Grant Date Fair Value Per Share, granted (in dollars per share) | $ / shares	$ 0
Vested (in shares) | shares	(81,000)
Weighted-Average Grant Date Fair Value Per Share, vested (in dollars per share) | $ / shares	$ 23.57
Forfeited (in shares) | shares	(3,000)
Weighted-Average Grant Date Fair Value Per Share, forfeited (in dollars per share) | $ / shares	$ 68.48
Ending balance (in shares) | shares	1,802,000
Weighted-Average Grant Date Fair Value Per Share, ending balance (in dollars per share) | $ / shares	$ 38.21
[1]	Amount reflects the number of awards that may ultimately be earned based on management's probability assessment of the achievement of performance conditions at each reporting period.

Note 3 - Stock-based Compensa_6

Note 3 - Stock-based Compensation - Valuation Assumptions (Details) - 2004 Employee Stock Plan [Member] - Employee Stock Purchase Plan [Member]	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Expected term (Year)	6 months	6 months
Expected volatility	31.40%	37.30%
Risk-free interest rate	1.60%	2.50%
Dividend yield	1.10%	1.20%

Note 4 - Balance Sheet Compon_3

Note 4 - Balance Sheet Components - Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Raw materials	$ 32,502	$ 22,872
Work in process	48,022	42,681
Finished goods	50,975	61,947
Total	$ 131,499	$ 127,500

Note 4 - Balance Sheet Compon_4

Note 4 - Balance Sheet Components - Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
RSU tax withholding proceeds receivable	$ 5,744	$ 6,106
Prepaid expense	18,444	7,991
Accrued interest receivable	2,530	2,490
Assets for product returns	1,824	1,585
Other	1,137	1,433
Total	$ 29,679	$ 19,605

Note 4 - Balance Sheet Compon_5

Note 4 - Balance Sheet Components - Other Long-term Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Deferred compensation plan assets	$ 35,547	$ 38,858
Operating lease right-of-use (“ROU”) assets	2,744	2,863
Prepaid expense	2,715	2,687
Other	1,457	1,544
Total	$ 42,463	$ 45,952

Note 4 - Balance Sheet Compon_6

Note 4 - Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Dividends and dividend equivalents	$ 27,846	$ 21,747
Stock rotation and sales returns	6,474	5,530
Accrued purchases of property and equipment	5,834	4,678
Income tax payable	2,462	2,435
Customer prepayments	5,221	3,412
Commissions	2,191	1,425
Warranty	1,144	1,139
Other	3,798	3,170
Total	56,110	44,790
Accrued Liabilities, Current [Member]
Operating lease liabilities	$ 1,140	$ 1,254

Note 4 - Balance Sheet Compon_7

Note 4 - Balance Sheet Components - Other Long-term Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Deferred compensation plan liabilities	$ 36,627	$ 39,665
Dividend equivalents	6,481	6,265
Other	29	30
Total	44,223	47,063
Other Long-term Liabilities [Member]
Operating lease liabilities	$ 1,086	$ 1,103

Note 5 - Leases (Details Textua

Note 5 - Leases (Details Textual) - USD ($) $ in Thousands	Jan. 01, 2019	Mar. 31, 2020		Mar. 31, 2019		Dec. 31, 2019
Operating Lease, Right-of-Use Asset		$ 2,744				$ 2,863
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 2,200	277	[1]	$ 2,264	[1]
Operating Lease, Lease Income, Lease Payments		400		$ 200
Other Assets [Member]
Operating Lease, Right-of-Use Asset		2,700				2,900
Other Liabilities [Member]
Operating Lease, Liability, Total		$ 2,200				$ 2,400
Maximum [Member]
Lessee, Operating Lease, Remaining Lease Term (Year)		4 years
Lessee, Operating Lease, Renewal Term (Year)		5 years
Lessor, Remaining Lease Term (Year)		5 years
Lessor, Operating Lease, Renewal Term (Year)		5 years
Minimum [Member]
Lessee, Operating Lease, Remaining Lease Term (Year)		1 year
Lessor, Remaining Lease Term (Year)		1 year
[1]	For the three months ended March 31, 2019, the amount includes $2.2 million for operating leases existing on January 1, 2019.

Note 5 - Leases - Leases Cost (

Note 5 - Leases - Leases Cost (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Mar. 31, 2020		Mar. 31, 2019		Dec. 31, 2019
Operating lease costs		$ 366		$ 305
Short-term and other lease costs		77		98
Total lease costs		443		403
Operating cash flows from operating leases		373		304
ROU assets obtained in exchange for new operating lease liabilities (1)	$ 2,200	$ 277	[1]	$ 2,264	[1]
Weighted-average remaining lease term (in years) (Year)		2 years 2 months 12 days				2 years 1 month 6 days
Weighted-average discount rate		3.60%				3.70%
[1]	For the three months ended March 31, 2019, the amount includes $2.2 million for operating leases existing on January 1, 2019.

Note 5 - Leases - Maturities of

Note 5 - Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
2020 (remaining nine months)	$ 994
2021	774
2022	453
2023	96
2024	12
Total remaining lease payments	2,329
Less: imputed interest	(103)
Accrued Liabilities and Other Long-term Liabilities [Member]
Total lease liabilities	2,226
Accrued Liabilities, Current [Member]
Current liabilities	1,140	$ 1,254
Other Long-term Liabilities [Member]
Long-term liabilities	$ 1,086	$ 1,103

Note 5 - Leases - Maturities _2

Note 5 - Leases - Maturities of Income Related to Lease Payments (Details) $ in Thousands	Mar. 31, 2020USD ($)
2020 (remaining nine months)	$ 1,620
2021	2,285
2022	2,074
2023	1,240
2024	552
Thereafter	59
Total	$ 7,830

Note 6 - Net Income Per Share -

Note 6 - Net Income Per Share - Net Income Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income	$ 35,756	$ 26,181
Denominator:
Weighted-average outstanding shares - basic (in shares)	44,455	42,749
Effect of dilutive securities (in shares)	2,215	2,483
Weighted-average outstanding shares - diluted (in shares)	46,670	45,232
Net income per share:
Earnings per share, basic (in dollars per share)	$ 0.80	$ 0.61
Earnings per share, diluted (in dollars per share)	$ 0.77	$ 0.58

Note 7 - Segment, Significant_3

Note 7 - Segment, Significant Customers and Geographic Information (Details Textual)	3 Months Ended
	Mar. 31, 2020
Number of Reportable Segments	1

Note 7 - Segment, Significant_4

Note 7 - Segment, Significant Customers and Geographic Information - Customers with Sales and Accounts Receivable Greater Than 10% (Details) - Customer Concentration Risk [Member]	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenue Benchmark [Member]
Concentration risk	80.00%	84.00%
Revenue Benchmark [Member] | Distributor A [Member]
Concentration risk	23.00%	23.00%
Revenue Benchmark [Member] | Customer A (Direct) [Member]
Concentration risk	10.00%
Accounts Receivable [Member] | Distributor A [Member]
Concentration risk	28.00%		24.00%
Accounts Receivable [Member] | Distributor B [Member]
Concentration risk	13.00%		11.00%
Accounts Receivable [Member] | Value Added Reseller A [Member]
Concentration risk	16.00%		13.00%

Note 7 - Segment, Significant_5

Note 7 - Segment, Significant Customers and Geographic Information - Revenue by Region (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue	$ 165,778	$ 141,363
CHINA
Revenue	105,737	76,198
TAIWAN, PROVINCE OF CHINA
Revenue	16,540	21,347
Europe [Member]
Revenue	13,072	12,984
KOREA, REPUBLIC OF
Revenue	10,944	9,611
South East Asia [Member]
Revenue	8,780	8,672
JAPAN
Revenue	6,890	6,642
UNITED STATES
Revenue	3,737	5,806
Other Region [Member]
Revenue	$ 78	$ 103

Note 7 - Segment, Significant_6

Note 7 - Segment, Significant Customers and Geographic Information - Revenue by Product Family (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue	$ 165,778	$ 141,363
DC To DC Products [Member]
Revenue	156,875	132,711
Lighting Control Products [Member]
Revenue	$ 8,903	$ 8,652

Note 7 - Segment, Significant_7

Note 7 - Segment, Significant Customers and Geographic Information - Long Lived Assets by Geographic Region (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Long lived assets by region	$ 236,807	$ 228,315
CHINA
Long lived assets by region	119,904	113,888
UNITED STATES
Long lived assets by region	96,982	94,671
TAIWAN, PROVINCE OF CHINA
Long lived assets by region	17,341	17,652
Other Region [Member]
Long lived assets by region	$ 2,580	$ 2,104

Note 8 - Commitments and Cont_3

Note 8 - Commitments and Contingencies (Details Textual) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Purchase Obligation, Total	$ 102.6
Minimum [Member]
Warranty Period (Year)	1 year
Maximum [Member]
Warranty Period (Year)	2 years

Note 8 - Commitments and Cont_4

Note 8 - Commitments and Contingencies - Changes in Warranty Reserve (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Balance	$ 1,139	$ 4,564
Warranty provision for product sales	541	268
Settlements made	(111)	(2,271)
Unused warranty provision	(425)	(516)
Balance	$ 1,144	$ 2,045

Note 9 - Cash, Cash Equivalen_3

Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash (Details Textual) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale, Total	$ 0	$ 0
Auction Rate Securities Maturities (Year)		26 years
Redemption, Auction Rate Securities to Date	$ 40,100
Percentage of Auction Rate Securities Redeemed at Par Value	93.00%

Note 9 - Cash, Cash Equivalen_4

Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash - Cash Equivalents, Short-term and Long-term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Cash	$ 143,926	$ 144,860
Money market funds	10,954	28,100
Commercial paper	4,943	1,994
U.S. treasuries and government agency bonds	20,534	19,493
Total	492,323	458,535
Cash and cash equivalents	154,880	172,960
Short-term investments	334,386	282,437
Long-term investments	3,057	3,138
Corporate Debt Securities [Member]
Available-for-sale securities	308,909	260,950
Auction Rate Securities [Member]
Available-for-sale securities	$ 3,057	$ 3,138

Note 9 - Cash, Cash Equivalen_5

Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash - Investment Maturity Classification (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Due in less than 1 year	$ 175,874	$ 175,281
Due in 1 - 5 years	159,928	159,105
Due in greater than 5 years	3,220	3,057
Total	$ 339,022	$ 337,443

Note 9 - Cash, Cash Equivalen_6

Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash - Unrealized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Amortized Cost	$ 349,976	$ 313,546
Unrealized Gains	603	390
Unrealized Losses	(2,182)	(261)
Total Fair Value	348,397	313,675
Money Market Funds [Member]
Amortized Cost	10,954	28,100
Unrealized Gains	0	0
Unrealized Losses	0	0
Total Fair Value	10,954	28,100
Corporate Debt Securities [Member]
Amortized Cost	310,367	260,645
Unrealized Gains	559	383
Unrealized Losses	(2,017)	(78)
Total Fair Value	308,909	260,950
Commercial Paper [Member]
Amortized Cost	4,942	1,994
Unrealized Gains	3	0
Unrealized Losses	(2)	0
Total Fair Value	4,943	1,994
US Government Agencies Short-term Debt Securities [Member]
Amortized Cost	20,493	19,487
Unrealized Gains	41	7
Unrealized Losses	0	(1)
Total Fair Value	20,534	19,493
Auction Rate Securities [Member]
Amortized Cost	3,220	3,320
Unrealized Gains	0	0
Unrealized Losses	(163)	(182)
Total Fair Value	$ 3,057	$ 3,138

Note 9 - Cash, Cash Equivalen_7

Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash - Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Continuous Unrealized Loss Position, Less than 12 Months	$ 217,538	$ 83,119
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,019)	(64)
Continuous Unrealized Loss Position, 12 Months or Longer	3,057	14,274
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(163)	(197)
Unrealized Loss Position, Total	220,595	97,393
Unrealized Loss Position, Accumulated Loss, Total	(2,182)	(261)
Corporate Debt Securities [Member]
Continuous Unrealized Loss Position, Less than 12 Months	215,069	82,126
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,017)	(63)
Continuous Unrealized Loss Position, 12 Months or Longer	0	11,136
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(15)
Unrealized Loss Position, Total	215,069	93,262
Unrealized Loss Position, Accumulated Loss, Total	(2,017)	(78)
Commercial Paper [Member]
Continuous Unrealized Loss Position, Less than 12 Months	2,469
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2)
Continuous Unrealized Loss Position, 12 Months or Longer	0
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Unrealized Loss Position, Total	2,469
Unrealized Loss Position, Accumulated Loss, Total	(2)
US Government Agencies Short-term Debt Securities [Member]
Continuous Unrealized Loss Position, Less than 12 Months		993
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(1)
Continuous Unrealized Loss Position, 12 Months or Longer		0
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Unrealized Loss Position, Total		993
Unrealized Loss Position, Accumulated Loss, Total		(1)
Auction Rate Securities [Member]
Continuous Unrealized Loss Position, Less than 12 Months	0	0
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Continuous Unrealized Loss Position, 12 Months or Longer	3,057	3,138
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(163)	(182)
Unrealized Loss Position, Total	3,057	3,138
Unrealized Loss Position, Accumulated Loss, Total	$ (163)	$ (182)

Note 9 - Cash, Cash Equivalen_8

Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash - Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash and cash equivalents	$ 154,880	$ 172,960
Restricted cash included in other long-term assets	116	116
Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows	$ 154,996	$ 173,076	$ 181,882	$ 172,818

Note 10 - Fair Value Measurem_3

Note 10 - Fair Value Measurements - Financial Assets and Liabilities, Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Total Fair Value	$ 348,397	$ 313,675
Assets, fair value	368,623	335,650
Fair Value, Inputs, Level 1 [Member]
Assets, fair value	31,180	50,075
Fair Value, Inputs, Level 2 [Member]
Assets, fair value	334,386	282,437
Fair Value, Inputs, Level 3 [Member]
Assets, fair value	3,057	3,138
Money Market Funds [Member]
Total Fair Value	10,954	28,100
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	10,954	28,100
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	0	0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	0	0
Corporate Debt Securities [Member]
Total Fair Value	308,909	260,950
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	0	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	308,909	260,950
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	0	0
Commercial Paper [Member]
Total Fair Value	4,943	1,994
Commercial Paper [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	0	0
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	4,943	1,994
Commercial Paper [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	0	0
US Government Agencies Short-term Debt Securities [Member]
Total Fair Value	20,534	19,493
US Government Agencies Short-term Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	0	0
US Government Agencies Short-term Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	20,534	19,493
US Government Agencies Short-term Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	0	0
Auction Rate Securities [Member]
Total Fair Value	3,057	3,138
Auction Rate Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	0	0
Auction Rate Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	0	0
Auction Rate Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	3,057	3,138
Mutual Fund [Member]
Total Fair Value	20,226	21,975
Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	20,226	21,975
Mutual Fund [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	0	0
Mutual Fund [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	$ 0	$ 0

Note 10 - Fair Value Measurem_4

Note 10 - Fair Value Measurements - Level 3 Investments (Details) - Auction Rate Securities [Member] $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Balance, auction rate securities	$ 3,138
Change in unrealized gain (loss) included in other comprehensive income	19
Sale and settlement at par	(100)
Balance, auction rate securities	$ 3,057

Note 10 - Fair Value Measurem_5

Note 10 - Fair Value Measurements - Discounted Cash Flow Assumptions (Details)		3 Months Ended	12 Months Ended
		Mar. 31, 2020	Dec. 31, 2019
Minimum [Member]
Time-to-liquidity (Year)		2 years	2 years
Discount rate		3.10%	4.00%
Maximum [Member]
Time-to-liquidity (Year)		3 years	3 years
Discount rate		7.30%	8.30%
Weighted Average [Member]
Time-to-liquidity (Year)	[1]	2 years 6 months
Discount rate	[1]	(5.00%)
[1]	The parenthetical information represents the weighted-average values, which were calculated based on the relative fair value of the securities.

Note 11 - Deferred Compensati_3

Note 11 - Deferred Compensation Plan - Summary of Deferred Compensation Plan (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Deferred compensation plan assets	$ 35,547	$ 38,858
Deferred compensation plan liabilities	36,782	40,090
Other Long-term Assets [Member]
Deferred compensation plan assets	35,547	38,858
Accrued Compensation and Related Benefits [Member]
Deferred compensation plan liabilities	155	425
Other Long-term Liabilities [Member]
Deferred compensation plan liabilities	36,627	39,665
Cash Surrender Value [Member]
Deferred compensation plan assets	15,321	16,883
Mutual Funds and Money Market Funds, Fair Value [Member]
Deferred compensation plan assets	$ 20,226	$ 21,975

Note 12 - Other Income (Expen_3

Note 12 - Other Income (Expense), Net - Interest and Other Income Components (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Interest income	$ 2,374	$ 1,696
Amortization of premium on available-for-sale securities	(494)	(121)
Gain (loss) on deferred compensation plan investments	(3,750)	1,935
Foreign currency exchange gain (loss)	3	(201)
Other	153	32
Total	$ (1,714)	$ 3,341

Note 13 - Income Taxes (Details

Note 13 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Expense (Benefit), Total	$ (6,484)	$ (1,123)
Effective Income Tax Rate Reconciliation, Percent, Total	22.20%	4.50%

Note 14 - Accumulated Other C_3

Note 14 - Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Income (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Balance	$ 773,491
Balance	813,190
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Balance	135
Other comprehensive income (loss) before reclassifications	(1,680)
Amounts reclassified from accumulated other comprehensive income (loss)	(28)
Tax effect	55
Net current period other comprehensive income (loss)	(1,653)
Balance	(1,518)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Balance	(5,611)
Other comprehensive income (loss) before reclassifications	(2,882)
Amounts reclassified from accumulated other comprehensive income (loss)	0
Tax effect	0
Net current period other comprehensive income (loss)	(2,882)
Balance	(8,493)
AOCI Attributable to Parent [Member]
Balance	(5,476)
Other comprehensive income (loss) before reclassifications	(4,562)
Amounts reclassified from accumulated other comprehensive income (loss)	(28)
Tax effect	55
Net current period other comprehensive income (loss)	(4,535)
Balance	$ (10,011)

Note 15 - Dividends and Divid_3

Note 15 - Dividends and Dividend Equivalents (Details Textual) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Dividends Payable, Current	$ 22.3	$ 17.4
Accrued Dividend Equivalents	$ 12	$ 10.6

Note 15 - Dividends and Divid_4

Note 15 - Dividends and Dividend Equivalents - Cash Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Dividend declared per share (in dollars per share)	$ 0.50	$ 0.40
Total amount	$ 22,317	$ 17,180